Intrauterine lead exposure and preterm birth

Social cost of mining-related lead (Pb) pollution in Kabwe, Zambia, and potential remediation measures

Lead (Pb) pollution has been one of the major environmental problems of worldwide significance. It is a latent factor for several fatal illnesses, whereas the exposure to lead in early childhood causes a lifetime IQ loss. The social cost is the concept to aggregate various adverse effects in a single monetary unit, which is useful in describing the pollution problem and provides foundation for the design of interventions. However, the assessment of the social cost is scarce for developing countries. In this study, we focus on the lead pollution problem of a former mining town, Kabwe, Zambia, where mining wastes abandoned near residential areas has caused a critical pollution problem. We first investigated the social cost of lead pollution that future generations born in 2025-2049 would incur in their lifetime. As the channels of the social cost, we considered the lost income from the IQ loss and the lost lives from lead-related mortality. The results showed that the social cost would amount to 224-593 million USD (discounted to the present value). Our results can be considered conservative, lower bound estimates because we focused only on well-identified effects of lead, but the social cost was still substantial. Then we examined several engineering remediation measures. The results showed that the social cost can be reduced (the benefits of remediations) more than the costs of implementing remediation measures. This study is the first to investigate the social cost of mining-related lead pollution problem in developing countries. Our interdisciplinary approach utilises the micro-level economic, health and pollution data and integrates the techniques in economics, toxicology and engineering.

A Data Mining Approach Reveals Chemicals Detected at Higher Levels in Non-Hispanic Black Women Target Preterm Birth Genes and Pathways

Preterm birth occurs disproportionately in the USA non-Hispanic Black population. Black women also face disproportionate exposure to certain environmental chemicals. The goal of this study was to use publicly available toxicogenomic data to identify chemical exposures that may contribute to preterm birth disparities. We tested 19 chemicals observed at higher levels in the blood or urine of non-Hispanic Black women compared to non-Hispanic White women. We obtained chemical-gene interactions from the Comparative Toxicogenomics Database and a list of genes involved in preterm birth from the Preterm Birth Database. We tested chemicals for enrichment with preterm birth genes using chi-squared tests. We then conducted pathway enrichment analysis for the preterm birth genes using DAVID software and identified chemical impacts on genes involved in these pathways. Genes annotated to all 19 chemicals were enriched with preterm birth genes (FDR-adjusted p value < 0.05). Preterm birth enriched chemicals that were detected at the highest levels in non-Hispanic Black women included methyl mercury, methylparaben, propylparaben, diethyl phthalate, dichlorodiphenyldichloroethylene, and bisphenol S. The preterm birth genes were enriched for pathways including "inflammatory response" (FDR-adjusted p value = 3 × 10-19), "aging" (FDR-adjusted p value = 4 × 10-8) and "response to estradiol" (FDR-adjusted p value = 2 × 10-4). Chemicals enriched with preterm birth genes impacted genes in all three pathways. This study adds to the body of knowledge suggesting that exposures to environmental chemicals contribute to racial disparities in preterm birth and that multiple chemicals drive these effects. These chemicals affect genes involved in biological processes relevant to preterm birth such as inflammation, aging, and estradiol pathways.

Maternal exposure to endocrine disrupting chemicals (EDCs) and preterm birth: A systematic review, meta-analysis, and meta-regression analysis

Preterm birth is the second most common cause of death in children under 5 years of age. The etiology of preterm birth has not yet been elucidated. Although maternal exposure to endocrine disrupting chemicals (EDCs) may increase the risk for preterm birth, associations have not been confirmed. We performed a meta-analysis to elucidate the relationships between maternal exposure to EDCs and preterm birth. A systematic search of PubMed, Ovid-EMBASE, and the Cochrane Library (CENTRAL) for relevant published studies providing quantitative data on the association between maternal EDC exposure and preterm birth in humans was conducted in July 2021. To calculate the overall estimates, we pooled the adjusted regression coefficients with 95% confidence intervals (CIs) from each study by the inverse variance method. A total of 59 studies were included. The pooled results indicated that maternal exposure to metals (OR, 1.23; 95% CI, 1.17 to 1.29) and phthalates (OR, 1.31; 95% CI, 1.21 to 1.42) was related to an increased risk for preterm birth. Specifically, maternal exposure to lead, cadmium, chromium, copper and manganese appeared to be correlated with an elevated risk for preterm birth. Additionally, maternal exposure to monoethyl phthalate (MEP), mono-2-ethyl-5-carboxypentyl phthalate (MECPP), monobenzyl phthalate (MBzP), and di (2-ethylhexyl) phthalate (DEHP) was also associated with preterm birth. In conclusion, maternal exposure to metals and phthalates may increase the risk for preterm birth based on current evidence.

Association of maternal lead exposure with the risk of preterm: a meta-analysis

BACKGROUND

The relationship between maternal lead level and risk of preterm birth (PTB) remained controversial. Therefore, herein we performed this meta-analysis to investigate the association of maternal blood, urine and cord blood lead level with the risk of PTB using observational studies.

METHODS

A systematic search was conducted in PubMed, EMBASE and Ovid Medline databases from inception to August 2019, and sixteen studies with 65600 participants investigating the association between maternal lead level and PTB were included in our meta-analysis. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated for the highest versus lowest lead level by random-effects model.

RESULTS

Overall, the pooled OR of all included articles for the highest versus lowest PTB score was 1.29 (95% CI = 1.14-1.46; I2 = 80.4%, p < .001), and the results revealed a direct and significant relationship between second and third trimester blood lead level (BLL) and PTB (OR 2nd trimester= 1.61, 95% CI = 1.08-2.40, OR 3rd trimester= 1.57, 95% CI = 1.11-2.23).

CONCLUSION

Results of this meta-analysis showed that maternal BLL is directly associated with the risk of PTB.

Maternal Urinary Metal and Metalloid Concentrations in Association with Oxidative Stress Biomarkers

Metal exposure has been associated with a wide range of adverse birth outcomes and oxidative stress is a leading hypothesis of the mechanism of action of metal toxicity. We assessed the relationship between maternal exposure to essential and non-essential metals and metalloids in pregnancy and oxidative stress markers, and sought to identify windows of vulnerability and effect modification by fetal sex. In our analysis of 215 women from the PROTECT birth cohort study, we measured 14 essential and non-essential metals in urine samples at three time points during pregnancy. The oxidative stress marker 8-iso-prostaglandin F2α (8-iso-PGF2α) and its metabolite 2,3-dinor-5,6-dihydro-15-15-F2t-IsoP, as well as prostaglandin F2α (PGF2α), were also measured in the same urine samples. Using linear mixed models, we examined the main effects of metals on markers of oxidative stress as well as the visit-specific and fetal sex-specific effects. After adjustment for covariates, we found that a few urinary metal concentrations, most notably cesium (Cs) and copper (Cu), were associated with higher 8-iso-PGF2α with effect estimates ranging from 7.3 to 14.9% for each interquartile range, increase in the metal concentration. The effect estimates were generally in the same direction at the three visits and a few were significant only among women carrying a male fetus. Our data show that higher urinary metal concentrations were associated with elevated biomarkers of oxidative stress. Our results also indicate a potential vulnerability of women carrying a male fetus.

Seafood consumption is associated with higher follicular fluid arsenic (As) and mercury (Hg) concentrations in women undergoing in vitro fertilization (IVF)

Human exposure to non-essential toxic metals such as cadmium (Cd), mercury (Hg), and lead (Pb), and metalloids such as arsenic (As) commonly occurs through diet. Toxic trace element exposures have been reported in association with fertility and fecundity in epidemiologic studies even at low to moderate levels. While most previous studies employed blood and urine biomarkers of exposure, few have assessed toxic trace elements in ovarian follicular fluid (FF), which surrounds the developing oocyte and hence may better reflect concentrations potentially affecting reproductive outcomes. Our objective was to identify dietary predictors of FF toxic trace elements in n = 56 women (mean age: 38.3 years) undergoing in vitro fertilization (IVF) at the University of California at San Francisco. We determined As, Hg, Cd, and Pb in 197 FF specimens, collected on the day of oocyte retrieval, using inductively coupled plasma tandem mass spectrometry. A comprehensive food frequency questionnaire was used to assess the weekly and annual dietary "patterns" of participants. Consumption of specific seafood items and turkey were correlated with individual FF toxic trace elements. We also found that each unit higher seafood consumption in the past week dominated by mollusks, shrimp, and bass was associated with 60% higher FF As (95% confidence interval (CI): 25%, 105%) and FF Hg (95%CI: 7%, 136%) concentrations. Higher annual seafood consumption dominated by urchin, crab, and trout was associated with 16% higher FF As (95%CI: -2%, 38%) and 31% higher FF Hg (95%CI: 7%, 60%) concentrations per unit intake. No associations were noted between diet and Cd and Pb levels in FF. Overall, our results suggest that higher seafood consumption contributes to elevated levels of As and Hg in FF. These findings are consistent with previous IVF studies that assessed toxic trace element exposures in blood and urine. To our knowledge, this is the first study to report that diet might be a source of As, Hg, Cd, and Pb in FF.

Prenatal exposure to mixtures of heavy metals and neurodevelopment in infants at 6 months

BACKGROUND

Exposure to mixture of neurotoxic metals such as lead, mercury and cadmium occurs at a specific point of time. When exposed to metal mixtures, one metal may act as an agonist or antagonist to another metal. Thus, it is important to study the effects of exposure to a combination of metals on children's development using advance statistical methods.

OBJECTIVES

In this study, we explored the effects of prenatal metal exposure including lead, mercury and cadmium in early pregnancy (12-20 weeks), late pregnancy (>28 weeks), and at birth on neurodevelopment of infants at 6 months of age.

METHODS

We included 523 eligible mother-child pairs from the mothers and children environmental health (MOCEH) study, a prospective birth cohort study in Korea. We used linear regression, Bayesian kernel machine regression (BKMR) and generalized additive models (GAM), to evaluate the effects of exposure to metal mixtures on neurodevelopment of infants aged 6 months. The Korean version of Bayley scale of infant and toddler development-II was used to measure the child's neurodevelopment.

RESULTS

Linear regression models showed a significant negative effect of lead exposure during late pregnancy on the mental development index (MDI) [β = -2.51 (-4.92, -0.10)] scores of infants aged 6 months following co-exposure to mercury. Further, linear regression analysis showed a significant interaction between late pregnancy lead and mercury concentrations. BKMR analysis showed similar results as those obtained in linear regression models. These results were also replicated in the GAM. Stratification analysis showed that greater than 50 percentile concentration of mercury in late pregnancy potentiated the adverse effects of lead in late pregnancy on MDI [β = -4.33 (-7.66, -1.00)] and psychomotor development index (PDI) [β = -5.30 (-9.13, -1.46)] at 6 months of age. Prenatal cadmium exposure did not show a significant association with MDI and PDI at 6 months in the linear regression or BKMR analysis.

CONCLUSION

Based on all the statistical methods used, we demonstrated the effect of combined exposure to metals on the neurodevelopment of infants aged 6 months, with significant interaction between lead and mercury.

Exposure to 17 trace metals in pregnancy and associations with urinary oxidative stress biomarkers

BACKGROUND

Exposure to some toxic metals, such as lead and cadmium, has been associated with increased oxidative stress. However less is known about other metals and metal mixtures, especially in pregnant women who are a vulnerable population.

METHODS

To study the relationship between exposure to trace metals and oxidative stress, we analyzed a panel of 17 metals and two oxidative stress biomarkers (8-isoprostane and 8-hydroxydeoxyguanosine [8-OHdG]) in urine samples collected at ~26 weeks gestation from pregnant women in Boston (n = 380). We used linear regression models to calculate percent differences and 95% confidence intervals (CI) in oxidative stress markers for an interquartile range (IQR) increase in each urinary metal with adjustment for other metals. In addition, we applied principal components analysis (PCA) and Bayesian kernel machine regression (BKMR), to examine cumulative effects (within correlated groups of exposures as well as overall) and interactions.

RESULTS

We estimated 109% (95% CI: 47, 198) higher 8-isoprostane and 71% (95% CI: 45, 102) higher 8-OHdG with an IQR increase in urinary selenium (Se). We also estimated higher 8-isoprostane (47%, 95% CI: 20.5, 79.4) and 8-OHdG (15.3%, 95% CI: 5.09, 26.5) in association with urinary copper (Cu). In our PCA, we observed higher 8-isoprostane levels in association with the "essential" PC (highly loaded by Cu, Se, and Zinc). In BKMR analyses, we also estimated higher levels of both oxidative stress biomarkers with increasing Se and Cu as well as increasing levels of both oxidative stress biomarkers in association with cumulative concentrations of urinary trace metals.

CONCLUSION

We observed higher 8-isoprostane and 8-OHdG levels in association with urinary trace metals and elements, particularly Se and Cu, in linear models and using mixtures approaches. Additionally, increasing cumulative exposure to urinary trace metals was associated with higher levels of both oxidative stress biomarkers. The beneficial effects of these compounds should be carefully questioned.

Investigation of occupational exposure to lead and its relation with blood lead levels in electrical solderers

Occupational exposure to lead compounds can cause headache, nausea, encephalopathy, anemia, chronic muscle pain, and saturnism. Exposure to lead in women can affect fertility, and cause abortion or low IQ in the offspring. The aim of this study was to investigate occupational exposure to lead and its relation with blood lead levels in female electrical parts solderers. This cross-sectional (descriptive and analytical) study was carried out on 40 female solderers, working in two electrical parts manufacturing factories in Neyshabur city in 2017-2018. Occupational exposure to lead was determined by the OSHA 121 method, and the NIOSH 8003 method was used to determine the concentration of lead in blood. Lead in blood and air samples were determined by using a flame atomic absorption analyzer. Blood was measured using a Cell Dyn Hematology device. Data were analyzed using STATA 15. The mean age of the solderers was 35.42 ± 6.80 years, and their average work experience was 7.85 ± 5.60 years. Mean occupational exposure to lead was 0.09 ± 0.01 mg/m³, and the mean levels of lead in the blood of solderers were 10.59 ± 3.25 μg/dL. The mean of red blood cells (RBC) was 4.88 mil/uL, white blood cells (WBC) = 8.53 Tho/uL, hemoglobin = 14.02 g/dL, and hematocrit = 42.38%. There was a significant correlation between the concentrations of lead in air and the level of lead in workers' blood (p = 0.012, r = 0.31). The level of lead in the workers' respiratory region (β = 0.36, p = 0.033), body mass index (β = 0.25, p = 0.028), and the season of the year (β = 0.21, p = 0.019) were the strongest factors affecting blood lead levels. There was a significant relation between lead in workers' air and their blood, although all blood indices were in normal range. Using lead-free alloys and local ventilation systems, and reducing exposure times are recommended to decrease exposure to lead among solderers.

Urinary trace metals individually and in mixtures in association with preterm birth

One in ten infants born in the United States is born preterm, or prior to 37 weeks gestation. Exposure to elevated levels of metals, such as lead and arsenic, has been linked to higher risk of preterm birth (PTB), but consequences of lower levels of exposure and less studied metals are unclear. We examined the associations between 17 urinary trace metals individually and in mixtures in relation to PTB. The LIFECODES birth cohort enrolled pregnant women at <15 weeks gestation at Brigham and Women's Hospital in Boston. We selected cases of PTB (n = 99) and unmatched controls (n = 291) and analyzed urine samples for a panel of trace metals (median: 26 weeks gestation). We used logistic regression models to calculate the odds ratio (OR) for PTB and subtypes of PTB based on presentation at delivery. Subtypes included spontaneous and placental PTB. We used elastic net (ENET) regularization to identify individual metals or pairwise interactions that had the strongest associations with PTB, and principal components analysis (PCA) to identify classes of exposures associated with the outcome. We observed increased odds of PTB (OR: 1.41, 95% Confidence Interval [CI]: 1.12, 1.78) in association with an interquartile range difference in urinary copper (Cu). We also observed an increased OR for selenium (OR: 1.33, 95% CI: 0.98, 1.81). ENET selected Cu as the most important trace metal associated with PTB. PCA identified 3 principal components (PCs) that roughly reflected exposure to toxic metals, essential metals, and metals with seafood as a common source of exposure. PCs reflecting essential metals were associated with increased odds of overall and spontaneous PTB. Maternal urinary copper in the third trimester was associated with increased risk of PTB, and statistical analyses for mixtures indicated that after accounting for correlation this metal was the most important statistical predictor of the outcome.

Edible wild plants growing in contaminated floodplains: implications for the issuance of tribal consumption advisories within the Grand Lake watershed of northeastern Oklahoma, USA

Metal releases from the Tri-State Mining District (TSMD) that is located in southwestern Missouri, southeastern Kansas, and northeastern Oklahoma, have contaminated floodplain soils within the Neosho and Spring river watersheds of the Grand Lake watershed. Since the Oklahoma portion of the watershed lies within ten tribal jurisdictions, the potential accumulation of metals within plant species that are gathered and consumed by tribal members, as well as the resulting metal exposure risks to tribal human health, was a warranted concern for further investigation. Within this study, a total of 36 plant species that are commonly consumed by tribes were collected from floodplain areas that were previously demonstrated to have elevated soil metal concentrations relative to reference sites. A significant, positive correlation was shown for metal concentrations in plant tissues versus soil (n = 258; Cd: R = 0.72, p = 0.00; Pb: R = 0.52, p = 0.00; and Zn: R = 0.70, p = 0.00). Additionally, a significant difference in metal concentration distributions existed between reference and impacted plant samples (n = 210, p = 0.00 for all metals). These results proved that floodplain soils are a major contamination pathway for metal accumulation within plants, and the source of metal contamination is the result of mining releases from the TSMD. Metal accumulation within plants was found to vary according to specific metal and plant species. The lowest dietary exposure out of all plant organs sampled were associated with fruit, whereas the highest was associated with roots, stem/leaves, and low-lying leafy greens. Metals in plants were compared to weekly dietary intake limits established by the Joint FAO/WHO Expert Committee on Food Additives. Based on specific serving sizes established within this study for tribal children and adults, many plant species had sufficient concentrations to warrant tribal consumption restrictions within the floodplains of Elm Creek, Grand Lake, Lost Creek, Spring River, and Tar Creek. Importantly, these results highlighted the necessity for the issuance of plant consumption advisories for tribal communities in the watershed. A consumption restriction guide on the number of allowable servings of each species per week at specific streams was developed within this study for tribal children and adults. Results also demonstrated that soil metal concentrations do not need to be exceptionally elevated relative to reference sites in order for plants to accumulate sufficient metal concentrations to exceed dietary limits for one serving. Therefore, the exposure risk associated with the consumption of plants cannot be accurately predicted solely from metal concentrations within soils, but must be based on metal concentrations within specific plant tissues on a site-by-site basis. A weekly consumption scenario was created within this study in order to better understand the potential metal dietary exposures to child and adult tribal members who consume multiple servings of multiple plant species per day, as well as benthic invertebrates and fish from the watershed. These findings demonstrated that plants pose a greater consumption exposure risk for tribal members than benthic invertebrates or fish. Therefore, without the consideration of exposure risks associated with the consumption of plants within future human health risk assessments, tribal health risks will be severely underestimated.

Individual heavy metal exposure and birth outcomes in Shenqiu county along the Huai River Basin in China

Background: Exposure to heavy metals during pregnancy is an important risk factor for adverse birth outcomes. We aimed to investigate the current heavy metal exposure levels in cord blood from healthy pregnant women residing in the Huaihe River Basin, China, and examined the association between heavy metal levels and dietary habits and lifestyle factors. In this study, we measured the exposure levels of five heavy metals in the umbilical cord blood from 350 healthy pregnant women and administered 350 self-reported questionnaires regarding the general characteristics and dietary habits of those women. Methods: This study was undertaken in Shenqiu county, Henan province, which is in the area of the Huai River Basin, in a cohort of pregnant women and newborn babies in 2013-2014. We recruited a sample of 1000 pregnant women among those receiving prenatal examination, measured the real individual newborn exposure to heavy metals in serum by ICP-MS, collected information regarding the pregnant women with a questionnaire survey and obtained data on environmental quality from environmental protection agencies and the available literature. We estimated the daily individual exposure to heavy metals of all the 1000 participants throughout the pregnancy and recorded their birth outcomes after delivery. Then we analyzed the association between birth outcome and individual exposure to heavy metals. Results: 54 newborn children had birth defects. The geometric means of cord blood levels of As, Cd, Cr, Pb and Hg were measured at 0.92 ± 1.01 ng mL-1, 0.11 ± 0.17 ng mL-1, 4.57 ± 5.02 ng mL-1, 3.37 ± 3.81 ng mL-1 and 0.89 ± 1.69 ng mL-1 for subjects (n = 54) who gave birth to infants with birth defects and 0.43 ± 0.88 ng mL-1, 0.52 ± 3.86 ng mL-1, 1.94 ± 2.92 ng mL-1, 4.38 ± 4.96 ng mL-1 and 0.43 ± 0.91 ng mL-1 for subjects (n = 296) with healthy infants, respectively. The contents of all five heavy metals in the whole blood of both of these two groups were higher than the reference values of the Chinese general population (P < 0.001). Conclusions: The occurrence of birth defects was 15.4% in this cohort, and was correlated to exposure of parents to environments containing heavy metal contaminants in Shenqiu county in the Huai River Basin. The heavy metal exposure situation of the investigated population had serious effects in terms of reproductive defects in children. The specific link between newborn defects and environmental heavy metal contaminants suggested that contamination in pregnant women persisted over time, and that the exposure may have a long term effect.

Sexually Dimorphic Effects of Early-Life Exposures to Endocrine Disruptors: Sex-Specific Epigenetic Reprogramming as a Potential Mechanism

PURPOSE OF REVIEW

The genetic material of every organism exists within the context of regulatory networks that govern gene expression-collectively called the epigenome. Animal models and human birth cohort studies have revealed key developmental periods that are important for epigenetic programming and vulnerable to environmental insults. Thus, epigenetics represent a potential mechanism through which sexually dimorphic effects of early-life exposures such as endocrine-disrupting chemicals (EDCs) manifest.

RECENT FINDINGS

Several animal studies, and to a lesser extent human studies, have evaluated life-course sexually dimorphic health effects following developmental toxicant exposures; many fewer studies, however, have evaluated epigenetics as a mechanism mediating developmental exposures and later outcomes. To evaluate epigenetic reprogramming as a mechanistic link of sexually dimorphic early-life EDCs exposures, the following criteria should be met: (1) well-characterized exposure paradigm that includes relevant windows for developmental epigenetic reprogramming; (2) evaluation of sex-specific exposure-related epigenetic change; and (3) observation of a sexually dimorphic phenotype in either childhood, adolescence, or adulthood.

Heads in the sand: public health and ecological risks of lead-based bullets for wildlife shooting in Australia

Lead (Pb) is a toxic element banned from fuel, paint and many other products in most developed countries. Nonetheless, it is still widely used in ammunition, including rifle bullets, and Pb-based bullets are almost universally used in Australia. For decades, poisoning from Pb shot (shotguns) has been recognised as a cause of disease in waterfowl and Pb shot has been subsequently banned for waterfowl hunting in many jurisdictions. However, the risks posed by Pb-based bullets (rifles) have not been similarly recognised in Australia. Pb-based rifle bullets frequently fragment, contaminating the tissue of shot animals. Consuming this Pb-contaminated tissue risks harmful Pb exposure and, thus, the health of wildlife scavengers (carrion eaters) and humans and their companion animals who consume harvested meat (game eaters). In Europe, North America and elsewhere, the environmental and human health risks of Pb-based bullets are widely recognised, and non-toxic alternatives (e.g. copper-based bullets) are increasingly being used. However, Australia has no comparable research despite widespread use of shooting, common scavenging by potentially susceptible wildlife species, and people regularly consuming shot meat. We conclude that Australia has its collective ‘head in the sand’ on this pressing worldwide One Health issue. We present the need for urgent research into this field in Australia.

Mandates of maternity at a science museum, from should to must

A pregnancy exhibit at a science museum is an opportunity to research how medical advice is communicated and interpreted. This paper is about the Beginning of Life area of an exhibition called The Amazing You at the Tampa Museum of Science and Industry, where exhibits are prescriptive as well as descriptive. Expectant women are urged to deliver full-term, normal birthweight babies, by behaving according to prescribed medical norms. This study provides ethnographic descriptions of the exhibits, as well as insights from museum visitors who were interviewed. The exhibits, which emphasize fetal rights and maternal duties, are interpreted and critiqued by women visitors. As the exhibits climb towards greater realism (from euphemistic computer graphics to actual fetal specimens) visitors encounter assertions of fact that precede sometimes tacit directives to undergo a medicalized pregnancy. Exhibits are viewed from the perspective of speech act theory, presenting a new approach to health communication research. I argue that this science center exhibit tells people what to do, in addition to passing on information.

Reduction of in utero lead exposures in South African populations: Positive impact of unleaded petrol

Background

Prenatal exposure to lead (Pb) has been shown to have negative and irreversible health impacts on foetal and early childhood development, affecting morbidity and mortality in adulthood. This study aimed to assess in utero Pb exposure, examine birth outcomes, and identify confounding factors in the large cohort of South African population, following the legislated removal of Pb from petrol.

Methods

Lead was measured in the maternal blood, urine and cord blood using Inductive Coupled Plasma Mass spectrometry (ICP-MS). The statistical analyses included Spearman’s correlation, Wilcoxon rank sum (Mann Whitney), Kruskal-Wallis rank tests and multivariate linear regression.

Results

Overall, the geometric mean (GM) of Pb in maternal blood (PbB) was 1.32 μg/dL (n = 640; 95% CI, 1.24–1.40). In the subset cohort, the GM of paired maternal PbB and cord blood (PbC) was 1.73 μg/dL (n = 350; 95% CI, 1.60–1.86) and 1.26 μg/dL (n = 317; 95% CI, 1.18–1.35), respectively with a positive correlation between the log PbB and the log PbC (rho = 0.65, p = <0.001). Birth outcomes showed geographical differences in the gestational age (p<0.001), birth length (p = 0.028) and head circumference (p<0.001), Apgar score at 5 min (p<0.001) and parity (p<0.002). In female neonates, a positive association was found between PbC and head circumference (rho = 0.243; p<0.016). The maternal PbB levels were positively correlated with race, educational status, water sources, cooking fuels and use of pesticides at home.

Conclusions

This study has demonstrated not only the positive impact that the introduction of unleaded petrol and lead-free paint has had on in utero exposure to Pb in South Africa, but has also contributed new data on the topic, in a region where such data and scientific investigations in this field are lacking. Future research should evaluate if similar effects can be detected in young children and the adult population.

Exposure to endocrine disruptors during adulthood: consequences for female fertility

Endocrine disrupting chemicals are ubiquitous chemicals that exhibit endocrine disrupting properties in both humans and animals. Female reproduction is an important process, which is regulated by hormones and is susceptible to the effects of exposure to endocrine disrupting chemicals. Disruptions in female reproductive functions by endocrine disrupting chemicals may result in subfertility, infertility, improper hormone production, estrous and menstrual cycle abnormalities, anovulation, and early reproductive senescence. This review summarizes the effects of a variety of synthetic endocrine disrupting chemicals on fertility during adult life. The chemicals covered in this review are pesticides (organochlorines, organophosphates, carbamates, pyrethroids, and triazines), heavy metals (arsenic, lead, and mercury), diethylstilbesterol, plasticizer alternatives (di-(2-ethylhexyl) phthalate and bisphenol A alternatives), 2,3,7,8-tetrachlorodibenzo-p-dioxin, nonylphenol, polychlorinated biphenyls, triclosan, and parabens. This review focuses on the hypothalamus, pituitary, ovary, and uterus because together they regulate normal female fertility and the onset of reproductive senescence. The literature shows that several endocrine disrupting chemicals have endocrine disrupting abilities in females during adult life, causing fertility abnormalities in both humans and animals.

The association of lead exposure during pregnancy and childhood anthropometry in the Mexican PROGRESS cohort

Lead exposure during pregnancy remains a public health problem with potential lifelong impacts on children's growth and development. Mexico is unique in that stunting and obesity are both major public health concerns in children. This situation might be exacerbated by lead exposure which remains more common in Mexico than in the United States due in part to the use of lead glazed pottery in food preparation and storage. Our objective is to determine how lead exposure during pregnancy is associated with children's growth parameters, including height, weight, body mass index and percentage body fat measured between ages 4-6 years old in a Mexico City pregnancy cohort. Blood lead was collected in the 2nd and 3rd trimester of pregnancy as well as at delivery. Bone lead was assessed in mothers as a long term exposure biomarker. We performed multivariable linear regression analyses to assess the association between each of these lead exposure biomarkers and child anthropometry. We found a significant negative association between maternal 3rd trimester blood lead concentration and offspring height for age (β-0.10; 95% CI -0.19, -0.01), and a negative association between maternal 3rd trimester blood lead concentration and weight for age (β-0.11; 95% CI -0.22,-0.003). Our results in this Mexican population add to previous findings of an association of lead and decreased stature and weight in early childhood. Ongoing follow-up and longitudinal analyses may help elucidate how this impacts growth trajectory and other children's health outcomes.

Occupational, Environmental, and Lifestyle Factors and their Contribution to Preterm Birth - An Overview

Preterm birth (PTB) is a significant public health concern and a leading cause of infant mortality and morbidity worldwide and often contributes to various health complications later in life. More than 60% of PTBs occur in Africa and south Asia. This overview discusses the available information on occupational, environmental, and lifestyle factors and their contribution to PTB and proposes new etiological explanations that underlie this devastating pregnancy complication. Several factors such as emotional, stress, social, racial, maternal anxiety, multiple pregnancies, infections during pregnancy, diabetes and high blood pressure, and in-vitro fertilization pregnancy have been shown to be associated with PTB. Data are emerging that occupational, environmental exposure and lifestyle factors might also be associated in part with PTB, however, they are at best limited and inconclusive. Nevertheless, data on heavy metals such as lead, air pollutants and particulate matters, bisphenol A, phthalate compounds, and environmental tobacco smoke (ETS) are promising and point to higher incidence of PTB associated with exposure to them. Thus, these observations can be used to advise pregnant women or women of reproductive age to avoid such exposures and adopt positive lifestyle to protect pregnancy and normal fetal development. There is a need to conduct well-planned epidemiological studies that include all the pathology causing factors that may contribute to adverse pregnancy outcomes, including PTB.

Potential sources and racial disparities in the residential distribution of soil arsenic and lead among pregnant women

Exposure to arsenic (As) or lead (Pb) has been associated with adverse health outcomes, and high-risk populations can be disproportionately exposed to these metals in soils. The objectives of this study were: to examine if predicted soil As and Pb concentrations at maternal residences of South Carolina (SC) low-income mothers differed based on maternal race (non-Hispanic black versus white), to examine whether differences in predicted residential soil As and Pb concentrations among black and white mothers differed by socioeconomic status (SES), and to examine whether such disparities persisted after controlling for anthropogenic sources of these metals, including direction from, and distance to industrial facilities. Kriged soil As and Pb concentrations were estimated at maternal residences in 11 locations in SC, and models with maternal race and individual and US Census block group level SES measures were examined. US Environmental Protection Agency Toxics Release Inventory (TRI) facility As and Pb releases categorized by distance and direction to block groups in which mothers resided were also identified, as were proxy measures for historic use of leaded gasoline (road density) and Pb-based paint (categories of median year home built by US Census block group). Consistent racial disparities were observed for predicted residential soil As and Pb concentrations, and the disparity was stronger for Pb than As (betas from adjusted models for black mothers were 0.12 and 2.2 for As and Pb, respectively, all p<0.006). Higher road density and older homes in block groups were more closely associated with higher predicted soil As and Pb concentrations than on-site releases of As and Pb categorized by facility location. These findings suggest that non-Hispanic black mothers in this study population had elevated residential As and Pb soil concentrations, after adjusting for SES, and that soil As and Pb concentrations were not associated with recent industrial releases.

Maternal blood lead concentrations, DNA methylation of MEG3 DMR regulating the DLK1/MEG3 imprinted domain and early growth in a multiethnic cohort

Prenatal exposure to lead (Pb) is known to decrease fetal growth; but its effects on postnatal growth and mechanistic insights linking Pb to growth are not clearly defined. Genomically imprinted genes are powerful regulators of growth and energy utilization, and may be particularly vulnerable to environmental Pb exposure. Because imprinting is established early and maintained via DNA methylation, we hypothesized that prenatal Pb exposure alters DNA methylation of imprinted genes resulting in lower birth weight and rapid growth. Pb was measured by inductively coupled plasma mass spectrometry (ICP-MS) in peripheral blood of 321 women of the Newborn Epigenetic STudy (NEST) obtained at gestation ~12 weeks. Linear and logistic regression models were used to evaluate associations between maternal Pb levels, methylation of differentially methylated regions (DMRs) regulating H19, MEG3, PEG3, and PLAGL1, measured by pyrosequencing, birth weight, and weight-for-height z score gains between birth and age 1yr, ages 1-2yrs, and 2-3yrs. Children born to women with Pb levels in the upper tertile had higher methylation of the regulatory region of the MEG3 DMR imprinted domain (β= 1.57, se= 0.82, p= 0.06). Pb levels were also associated with lower birth weight (β= -0.41, se= 0.15, p= 0.01) and rapid gains in adiposity (OR= 12.32, 95%CI=1.25-121.30, p= 0.03) by age 2-3 years. These data provide early human evidence for Pb associations with hypermethylation at the MEG3 DMR regulatory region and rapid adiposity gain-a risk factor for childhood obesity and cardiometabolic diseases in adulthood.

Prenatal exposure to lead in relation to risk of preterm low birth weight: A matched case-control study in China

We investigated the association between prenatal exposure to lead (Pb) and the risk of preterm low birth weight (PLBW). Pb concentrations in maternal urine collected at birth from 408 subjects (102 cases and 306 matched controls) were analyzed and adjusted by creatinine. The median Pb concentration in the PLBW cases (10.60μgPb/g creatinine) was higher than that of the controls (7.28μgPb/g creatinine). An adjusted odds ratio (OR) of 2.96 (95% CI=1.49-5.87) for PLBW was observed when the highest tertile was compared to the lowest tertile of Pb levels. The association was more pronounced among female infants (adjusted OR=3.67 for the highest tertile; 95% CI=1.35-9.93) than male infants (adjusted OR=1.91 for the highest tertile; 95% CI=0.74-4.95). Our study suggests that prenatal exposure to levels of Pb encountered today in China is associated with an elevated risk of PLBW.

Concentration of lead, mercury, cadmium, aluminum, arsenic and manganese in umbilical cord blood of Jamaican newborns

The objective of this study was to characterize the concentrations of lead, mercury, cadmium, aluminum, and manganese in umbilical cord blood of Jamaican newborns and to explore the possible association between concentrations of these elements and certain birth outcomes. Based on data from 100 pregnant mothers and their 100 newborns who were enrolled from Jamaica in 2011, the arithmetic mean (standard deviation) concentrations of cord blood lead, mercury, aluminum, and manganese were 0.8 (1.3 μg/dL), 4.4 (2.4 μg/L), 10.9 (9.2 μg/L), and 43.7 (17.7 μg/L), respectively. In univariable General Linear Models, the geometric mean cord blood aluminum concentration was higher for children whose mothers had completed their education up to high school compared to those whose mothers had any education beyond high school (12.2 μg/L vs. 6.4 μg/L; p < 0.01). After controlling for maternal education level and socio-economic status (through ownership of a family car), the cord blood lead concentration was significantly associated with head circumference (adjusted p < 0.01). Our results not only provide levels of arsenic and the aforementioned metals in cord blood that could serve as a reference for the Jamaican population, but also replicate previously reported significant associations between cord blood lead concentrations and head circumference at birth in other populations.

Evolution of DOHaD: the impact of environmental health sciences

Environmental exposures have a significant influence on the chronic health conditions plaguing children and adults. Although the Developmental Origins of Health and Disease (DOHaD) paradigm historically has focused on nutrition, an expanding body of research specifically communicates the effects of chemical exposures on early-life development and the propagation of non-communicable disease across the lifespan. This paper provides an overview of 20 years of research efforts aimed at identifying critical windows of susceptibility to environmental exposures and the signaling changes and epigenetic influences associated with disease progression. DOHaD grants funded by the National Institute of Environmental Health Sciences (NIEHS) in 1991, 2001 and 2011 are identified by grant-analysis software, and each portfolio is analyzed for exposures, disease endpoints, windows of exposure, study design and impact on the field based on publication data. Results show that the 1991 and 2001 portfolios comprised metals, PCBs and air pollutants; however, by 2011, the portfolio has evolved to include or expand the variety of endocrine disruptors, pesticides/persistent organic pollutants and metals. An assortment of brain-health endpoints is most targeted across the portfolios, whereas reproduction and cancer increase steadily over the same time period, and new endpoints like obesity are introduced by 2011. With mounting evidence connecting early-life exposures to later-life disease, we conclude that it is critical to expand the original DOHaD concept to include environmental chemical exposures, and to continue a research agenda that emphasizes defining sensitive windows of exposure and the mechanisms that cause disease.

Postnatal growth following prenatal lead exposure and calcium intake

BACKGROUND

The effects on postnatal growth of maternal exposure to low levels of lead during pregnancy have not been well established. In addition, information is limited regarding the protective effect of dietary calcium intake during pregnancy against the effect of lead for fetal and postnatal growth. We investigated the relationship between prenatal exposure to lead and growth at birth and 6, 12, and 24 months postnatal, and evaluated the role of calcium intake against the effect of lead.

METHODS

A total of 1150 pregnant women, and their subsequent offspring, enrolled in a prospective birth cohort study (Mothers and Children's Environmental Health Study), were evaluated. Multivariable regression analysis was conducted to estimate the effects of prenatal maternal blood lead levels on growth at each follow-up.

RESULTS

The blood lead levels of participating mothers were <5.0 μg/dL and mean levels were 1.25 μg/dL during the early (before 20 gestational weeks) and late (at delivery) gestational periods. Prenatal exposure to lead, particularly in late pregnancy, was significantly associated with a reduction in infantile growth at 24 months. When pregnant women had dietary calcium intake at mean or upper level, the association was not significant. In contrast, lower than mean level of calcium intake intensified the adverse effect of prenatal lead exposure on growth in children.

CONCLUSIONS

Prenatal lead exposure <5.0 μg/dL adversely affects postnatal growth and low calcium intake aggravates the effect, indicating more stringent control of lead and sufficient intake of calcium are necessary to help children's health.

Elevated blood lead levels among unskilled construction workers in Jimma, Ethiopia

Background

No study has been carried out to assess the blood lead levels of workers or the contribution of common workplace practices to lead exposure in Ethiopia. This study was carried out to assess the blood lead levels of female and male laborers in the construction sector in Jimma town, Ethiopia.

Method

A cross-sectional study on the blood lead levels of 45 construction workers was carried out in the town of Jimma. The t-test, analysis of variance, the Kruskal-Wallis, Mann–Whitney and odds ratio tests were used to compare mean blood lead levels and to investigate the associations between specific job type, use of self-protection device, sex, service years and occurrence of non-specific symptoms with BLLs.

Results

The mean blood lead level of the exposed group (40.03 ± 10.41 μg/dL) was found to be significantly greater than that of the unexposed group (29.81 ± 10.21 μg/dL), p = 0.05. Among the exposed group female workers were found to have higher mean blood lead level (42.04 ± 4.11 μg/dL) than their male colleagues (33.99 ± 3.28 μg/dL). Laborers who were regularly using self-protection devices were found to have significantly lower blood lead levels than those who were not using.

Conclusion

The blood lead levels of construction workers in Jimma town are considerably high with a range of 20.46 – 70.46 μg/dL and the workers are in danger of imminent lead toxicity. More endangered are female construction workers who are bearers of the future children of the country and the issue requires urgent attention.

Sources of potential lead exposure among pregnant women in New Mexico

The objectives of this study were to ascertain the prevalence and potential sources of lead exposure among pregnant women residing in a socially-disadvantaged immigrant community in Albuquerque, New Mexico. Pregnant women (n = 140) receiving prenatal care through a community clinic participated in a structured interview and screening to measure their blood lead levels (BLLs). Potential sources of lead exposure were ascertained by the CDC and New Mexico Department of Health questionnaires. Self-reported risk factors were examined as predictors of BLLs using multiple linear regression and partial least squares discriminant analysis. Most patients were Spanish-speaking (88.6%), Latina (95%), foreign-born (87.1%), lacked health insurance (86.4%), and had a high school education or lower (84.3%). While risk factors were prevalent in this population, only three women (2.1%) had BLLs ≥3 μg/dL. Results of multivariate analyses demonstrated that pica symptoms in pregnancy, history of elevated BLLs before pregnancy, use of non-commercial pottery, and living in older houses were important predictors of elevated BLLs. Although the prevalence of other risk factors relevant to immigrant communities (i.e., use of traditional/folk remedies and cosmetics, seasonings and food products from Mexico) was high, they were not predictive of elevated BLLs. Clinics providing prenatal care to immigrant Hispanic communities should carefully assess patients' pica symptoms, use of non-commercial pottery, and a history of elevated BLLs. Moreover, additional efforts need to focus on the development of screening questionnaires which better reflect exposures of concern in this population.

Could genetic polymorphisms related to oxidative stress modulate effects of heavy metals for risk of human preterm birth?

Human preterm birth (PTB) is a complex medical outcome influenced by a combination of genetic and environmental factors. Research on the causative factors of PTB has mostly focused on demographic, socio-behavioral and environmental risk factors. Recent studies turn the spotlight on the effects of heavy metals exposure on adverse pregnancy outcomes. Here we present and evaluate the hypothesis that heavy metals may cause PTB through oxidative stress, and that this effect may be modified by polymorphisms in genes related to oxidative stress. Indeed, accumulating data suggest that the risk of PTB is correlated with polymorphisms in genes involved in detoxification, oxidative stress and lipid metabolism. These and other polymorphisms have independently been associated with susceptibility to the adverse effects of heavy metals.

Environmental contaminant exposures and preterm birth: a comprehensive review

Preterm birth is a significant public health concern, as it is associated with high risk of infant mortality, various morbidities in both the neonatal period and later in life, and a significant societal economic burden. As many cases are of unknown etiology, identification of the contribution of environmental contaminant exposures is a priority in the study of preterm birth. This is a comprehensive review of all known studies published from 1992 through August 2012 linking maternal exposure to environmental chemicals during pregnancy with preterm birth. Using PubMed searches, studies were identified that examined associations between preterm birth and exposure to five categories of environmental toxicants, including persistent organic pollutants, drinking-water contaminants, atmospheric pollutants, metals and metalloids, and other environmental contaminants. Individual studies were summarized and specific suggestions were made for future work in regard to exposure and outcome assessment methods as well as study design, with the recommendation of focusing on potential mediating toxicological mechanisms. In conclusion, no consistent evidence was found for positive associations between individual chemical exposures and preterm birth. By identifying limitations and addressing the gaps that may have impeded the ability to identify true associations thus far, this review can guide future epidemiologic studies of environmental exposures and preterm birth.

Associations of estimated residential soil arsenic and lead concentrations and community-level environmental measures with mother-child health conditions in South Carolina

We undertook a community-level aggregate analysis in South Carolina, USA, to examine associations between mother-child conditions from a Medicaid cohort of pregnant women and their children using spatially interpolated arsenic (As) and lead (Pb) concentrations in three geographic case areas and a control area. Weeks of gestation at birth was significantly negatively correlated with higher estimated As (r(s) = -0.28, p = 0.01) and Pb (r(s) = -0.26, p = 0.02) concentrations in one case area. Higher estimated Pb concentrations were consistently positively associated with frequency of black mothers (all p < 0.02) and negatively associated with frequency of white mothers (all p < 0.01), suggesting a racial disparity with respect to Pb.

Environmental toxicant exposure during pregnancy

This literature review is meant to serve as a brief reference for acute and chronic poisonings in pregnant women, specifically involving environmental toxicants commonly present in the home or workplace. These scenarios are familiar to primary care providers but cause great confusion for practitioners and anxiety in the pregnant patient. Herein, we review metals and metalloids, organic solvents, disinfectant byproducts, pesticides, plasticizers, and multiple air pollutants. Reviews of specific studies involving these toxicants are provided to assist practitioners in providing information to patients regarding potential sources, mechanism of action, current laboratory and epidemiological studies, and possible treatments. Literature-based associations with specific toxicants and various pregnancy outcomes are also outlined. Finally, a contact list of important federal and state toxicology support services is provided.

TARGET AUDIENCE

Obstetricians & Gynecologists.

LEARNING OBJECTIVES

After completing this CME activity, physicians should be better able to assess both acute and chronic consequences of various environmental toxic exposures in pregnancy; to evaluate possible pregnancy related specific events surrounding environmental pollutants; and to identify common exposure routes and implement therapeutic interventions where appropriate.

Maternal low-level lead exposure and fetal growth

BACKGROUND

Limited epidemiologic studies have examined the association between maternal low-level lead exposure [blood lead (PbB) < 10 µg/dL] and fetal growth.

OBJECTIVE

We examined whether maternal low-level lead exposure is associated with decreased fetal growth.

METHODS

We linked New York State Heavy Metals Registry records of women who had PbB measurements with birth certificates to identify 43,288 mother-infant pairs in upstate New York in a retrospective cohort study from 2003 through 2005. We used multiple linear regression with fractional polynomials and logistic regression to relate birth weight, preterm delivery, and small for gestational age to PbB levels, adjusting for potential confounders. We used a closed-test procedure to identify the best fractional polynomials for PbB among 44 combinations.

RESULTS

We found a statistically significant association between PbB (square root transformed) and birth weight. Relative to 0 µg/dL, PbBs of 5 and 10 µg/dL were associated with an average of 61-g and 87-g decrease in birth weight, respectively. The adjusted odds ratio for PbBs between 3.1 and 9.9 µg/dL (highest quartile) was 1.04 [95% confidence interval (CI), 0.89-1.22] for preterm delivery and 1.07 (95% CI, 0.93-1.23) for small for gestational age, relative to PbBs ≤ 1 µg/dL (lowest quartile). No clear dose-response trends were evident when all of the quartiles were assessed.

CONCLUSIONS

Low-level PbB was associated with a small risk of decreased birth weight with a supralinear dose-response relationship, but was not related to preterm birth or small for gestational age. The results have important implications regarding maternal PbB.

Longitudinal study of prenatal and postnatal lead exposure and early cognitive development in Al-Kharj, Saudi Arabia: a preliminary results of cord blood lead levels

Extensive data shows a direct link between low-level lead exposure during early development and deficits in neurobehavioral-cognitive performance evident late in childhood through adolescence. Our previous studies confirmed the transfer of lead from the mother to the fetus as well as the effect of low lead exposure on neuropsychological behavior in school children. Such results led us to design a longitudinal survey to evaluate the effect of prenatal and/or postnatal lead exposure on early cognitive development among selected group of children from birth to 2 years of age. During the first stage of this study (between March and July 2004), we measured lead levels in 653 umbilical cord blood samples taken from healthy Saudi mothers delivering at King Khalid Hospital, Al-Kharj. This gave a good opportunity to look at the prevalence of increased blood lead levels in umbilical cord blood and to identify risk factors for prenatal lead exposure. The mean cord lead levels were 2.21 +/- 1.691 microg/dl in the range of 0.284-17.276 microg/dl. Only 1.23% of the newborns had blood lead levels >10 microg/dl, the Center for Disease Control level of concern. To investigate risk factors affecting cord blood lead levels, only subjects with lead levels above the 75th percentile (2.475 microg/dl) were selected in the multiple regression models. We observed that cord blood lead levels were significantly influenced by maternal age, the location of residence and intake of prenatal supplements. Controlling for newborn's head circumferences confounders, it was found that cord blood lead levels were significantly and negatively associated with newborn's head circumference (beta = -0.158, p = 0.036). The negative association was seen between intake of prenatal supplements and cord blood lead levels emphasizing the role of prenatal supplementations during pregnancy. The significant reductions in newborns, head circumferences due to lead exposure may have serious implications for their future performance and achievement. This study reveals that even at low prenatal lead exposure, all possible measures to inspect lead sources in our environment and reduce lead exposure should be taken.

Epidemiologic evidence of relationships between reproductive and child health outcomes and environmental chemical contaminants

This review summarizes the level of epidemiologic evidence for relationships between prenatal and/or early life exposure to environmental chemical contaminants and fetal, child, and adult health. Discussion focuses on fetal loss, intrauterine growth restriction, preterm birth, birth defects, respiratory and other childhood diseases, neuropsychological deficits, premature or delayed sexual maturation, and certain adult cancers linked to fetal or childhood exposures. Environmental exposures considered here include chemical toxicants in air, water, soil/house dust and foods (including human breast milk), and consumer products. Reports reviewed here included original epidemiologic studies (with at least basic descriptions of methods and results), literature reviews, expert group reports, meta-analyses, and pooled analyses. Levels of evidence for causal relationships were categorized as sufficient, limited, or inadequate according to predefined criteria. There was sufficient epidemiological evidence for causal relationships between several adverse pregnancy or child health outcomes and prenatal or childhood exposure to environmental chemical contaminants. These included prenatal high-level methylmercury (CH(3)Hg) exposure (delayed developmental milestones and cognitive, motor, auditory, and visual deficits), high-level prenatal exposure to polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans (PCDFs), and related toxicants (neonatal tooth abnormalities, cognitive and motor deficits), maternal active smoking (delayed conception, preterm birth, fetal growth deficit [FGD] and sudden infant death syndrome [SIDS]) and prenatal environmental tobacco smoke (ETS) exposure (preterm birth), low-level childhood lead exposure (cognitive deficits and renal tubular damage), high-level childhood CH(3)Hg exposure (visual deficits), high-level childhood exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (chloracne), childhood ETS exposure (SIDS, new-onset asthma, increased asthma severity, lung and middle ear infections, and adult breast and lung cancer), childhood exposure to biomass smoke (lung infections), and childhood exposure to outdoor air pollutants (increased asthma severity). Evidence for some proven relationships came from investigation of relatively small numbers of children with high-dose prenatal or early childhood exposures, e.g., CH(3)Hg poisoning episodes in Japan and Iraq. In contrast, consensus on a causal relationship between incident asthma and ETS exposure came only recently after many studies and prolonged debate. There were many relationships supported by limited epidemiologic evidence, ranging from several studies with fairly consistent findings and evidence of dose-response relationships to those where 20 or more studies provided inconsistent or otherwise less than convincing evidence of an association. The latter included childhood cancer and parental or childhood exposures to pesticides. In most cases, relationships supported by inadequate epidemiologic evidence reflect scarcity of evidence as opposed to strong evidence of no effect. This summary points to three main needs: (1) Where relationships between child health and environmental exposures are supported by sufficient evidence of causal relationships, there is a need for (a) policies and programs to minimize population exposures and (b) population-based biomonitoring to track exposure levels, i.e., through ongoing or periodic surveys with measurements of contaminant levels in blood, urine and other samples. (2) For relationships supported by limited evidence, there is a need for targeted research and policy options ranging from ongoing evaluation of evidence to proactive actions. (3) There is a great need for population-based, multidisciplinary and collaborative research on the many relationships supported by inadequate evidence, as these represent major knowledge gaps. Expert groups faced with evaluating epidemiologic evidence of potential causal relationships repeatedly encounter problems in summarizing the available data. A major driver for undertaking such summaries is the need to compensate for the limited sample sizes of individual epidemiologic studies. Sample size limitations are major obstacles to exploration of prenatal, paternal, and childhood exposures during specific time windows, exposure intensity, exposure-exposure or exposure-gene interactions, and relatively rare health outcomes such as childhood cancer. Such research needs call for investments in research infrastructure, including human resources and methods development (standardized protocols, biomarker research, validated exposure metrics, reference analytic laboratories). These are needed to generate research findings that can be compared and subjected to pooled analyses aimed at knowledge synthesis.

Are intrauterine growth restriction and preterm birth associated with dental caries?

OBJECTIVES

To assess the association between two intrauterine growth restriction (IUGR) surrogates - IUGR [small for gestational age birth (SGA) and fetal growth restriction (FGR)] and preterm birth with dental caries.

METHODS

Data from the Third National Health and Nutritional Examination Survey (1988-1994) were used, including 2- to 5.9-year-old singletons (n = 3189). Dental caries was defined as presence of any teeth with dental caries (treated or untreated) and also as presence of at least two teeth with dental caries. Exposure variables were preterm birth (<37 gestational weeks), FGR, and SGA. Covariates included were poverty, race/ethnicity, age, sex, sucrose intake, environmental tobacco smoking, dental visits, education of head of household, breastfeeding, and use of baby bottle. Separate statistical analyses were conducted for IUGR and for preterm birth through the estimation of prevalence ratio (PR), taking complex sampling design into consideration and adjusting for confounders. Sensitivity analysis was conducted including and excluding 2-year-old children and also with the two definitions of dental caries.

RESULTS

In general, the inclusion of 2-year-old children and the case definition of presence of any teeth with dental caries biased the results toward the null, but with no major changes in the results. In bivariate analysis, SGA and FGR birth were both negatively but not significantly associated with dental caries while a significant positive association was found for preterm birth. Sensitivity analysis showed that the PR for preterm in bivariate analysis varied from 1.65 (95% CI 1.14-2.40) to 1.84 (95% CI 1.19-2.83). After adjusting for confounders, the PR for preterm birth varied from 1.38 (95% CI 1.00-1.89) to 1.64 (95% CI 1.22-2.20). After adjustment, the PR for SGA varied from 0.79 (95% CI 0.56-101) to 0.66 (95% CI 0.33-0.96). For children from 3 to 5.9 years old, the adjusted PR for FGR using the category 'none' as reference were mild (PR 1.10; 95% CI 0.76-1.58), moderate (PR 0.66; 95% CI 0.26-167), and severe (PR 0.59; 95% CI 0.36-0.99). These values for FGR were very similar for the other models using other classifications of case definition or inclusion of 2-year-old children.

CONCLUSIONS

Preterm birth was found to be positively associated with dental caries while there is an indication that SGA and FGR are negatively associated with dental caries. Although the negative association is counterintuitive, it is possible that increased antibiotic use and delayed tooth eruption may explain the negative association between IUGR and dental caries.

Environmental hazards: evidence for effects on child health

The human fetus, child, and adult may experience adverse health outcomes from parental or childhood exposures to environmental toxicants. The fetus and infant are especially vulnerable to toxicants that disrupt developmental processes during relatively narrow time windows. This review summarizes knowledge of associations between child health and development outcomes and environmental exposures, including lead, methylmercury, polychlorinated biphenyls (PCBs), dioxins and related polyhalogenated aromatic hydrocarbons (PHAHs), certain pesticides, environmental tobacco smoke (ETS), aeroallergens, ambient air toxicants (especially particulate matter [PM] and ozone), chlorination disinfection by-products (DBPs), sunlight, power-frequency magnetic fields, radiofrequency (RF) radiation, residential proximity to hazardous waste disposal sites, and solvents. The adverse health effects linked to such exposures include fetal death, birth defects, being small for gestational age (SGA), preterm birth, clinically overt cognitive, neurologic, and behavioral abnormalities, subtle neuropsychologic deficits, childhood cancer, asthma, other respiratory diseases, and acute poisoning. Some environmental toxicants, notably lead, ionizing radiation, ETS, and certain ambient air toxicants, produce adverse health effects at relatively low exposure levels during fetal or child developmental time windows. For the many associations supported by limited or inadequate epidemiologic evidence, major sources of uncertainty include the limited number of studies conducted on specific exposure-outcome relationships and methodologic limitations. The latter include (1) crude exposure indices, (2) limited range of exposure levels, (3) small sample sizes, and (4) limited knowledge and control of potential confounders. Important knowledge gaps include the role of preconceptual paternal exposures, a topic much less studied than maternal or childhood exposures. Large longitudinal studies beginning before or during early pregnancy are urgently needed to accurately measure and assess the relative importance of parental and childhood exposures and evaluate relatively subtle health outcomes such as neuropsychologic and other functional deficits. Large case-control studies are also needed to assess the role of environmental exposures and their interactions with genetic factors in relatively uncommon outcomes such as specific types of birth defects and childhood cancers. There is also an urgent need to accelerate development and use of biomarkers of exposure and genetic susceptibility in epidemiologic studies. This review supports the priority assigned by international agencies to relationships between child health and air quality (indoor and outdoor), lead, pesticides, water contaminants, and ETS. To adequately address such priorities, governments and agencies must strengthen environmental health research capacities and adopt policies to reduce parental and childhood exposures to proven and emerging environmental threats.

Low blood lead concentration in association with infertility in women

This study investigated the relationship between low-level lead exposure and risk of infertility in women. Study participants consisted of 64 cases recruited at a private infertility clinic and 83 control women from the postpartum clinic unit at a medical center in Kaohsiung, Taiwan. With informed consent, venous blood samples were obtained from subjects, during their early follicular phases (the 1st to 5th days of the menstrual cycle), for measuring concentrations of lead and hormones. Information on other potential risk factors associated with infertility, including reproductive history, Chinese herbal Medicine use, dairy product consumption, residential environment, and sociodemographic status, was obtained during an in-person interview. The mean blood lead level (BLL) in infertile women was significantly higher than that in controls (3.55 vs 2.78 microg/dL, P=0.007). Compared to women with BLL < or = 2.5 microg/dL, women with BLL>2.5 microg/dL were associated with a threefold increased risk for infertility (adjusted odds ratio=2.94, 95% confidence interval 1.18-7.34), after controlling for age, body mass index, smoking, Chinese herbal Medicine use, and irregular menstruation. Women's BLL was a significant predictor of the serum estradiol concentration also. These findings suggest an important role of very low BLL in the risk of infertility in women.

Parental exposure to lead and small for gestational age births

BACKGROUND

Previous studies about the effect of lead exposure on adverse birth outcomes are still inconsistent and few studies estimate the relationship between parental lead exposure and small for gestational age (SGA) infants. An occupational cohort study to assess whether parental lead exposure would be related to decreased birth weight and shortened gestational ages of their offspring was conducted. Whether higher lead exposure doses would increase risks of low birth weight (LBW), preterm delivery, and SGA births was also investigated.

METHODS

A Program to Reduce Exposure by Surveillance System-Blood Lead Levels (Press-BLLS) was established in Taiwan in July 1993. The names of workers exposed to lead was collected from this occupational blood-lead notification database. The birth outcomes of their offspring were determined by linking to the Taiwan birth registration database from 1993 to 1997. Only singleton births whose parental blood-lead concentrations were tested during pregnancy or prior to conception, or within a 1-year span before these two periods were included.

RESULTS

Among 1,611 eligible births, 72 births were LBW, 74 were preterm deliveries, and 135 were SGA. Maternal blood-lead concentrations (PbBs) equal to or more than 20 microg/dl had a higher risk of mothering a SGA child (risk ratio (RR) = 2.15; 95% confidence interval (CI), 1.15-3.83).

CONCLUSIONS

Additional evidence of the effects of lead on adverse birth outcomes, especially for SGA births is reported. Maternal exposure to lead plays a more important role in the adverse effect on birth outcome than does paternal exposure.

Lead exposure and birth outcomes in five communities in Shoshone County, Idaho

INTRODUCTION

This study examined birth outcomes in five towns in Shoshone County, Idaho, where residents were exposed to high levels of lead in air emissions during a 6-month period after a fire had damaged the main baghouse (pollution-control device) of a local lead smelter plant in September 1973.

METHODS

We studied birth certificate data of 169,878 live singleton infants born to mothers who resided in Idaho at the time of delivery. The outcomes evaluated were preterm infants, small-for-gestational-age (SGA) infants, low birthweight among term infants (TLBW), and mean birthweight among term infants (TMBW). The study compared births in the five towns in Shoshone County (exposed group) to births in the rest of Idaho during three exposure periods: "pre-fire," January 1, 1970-August 31, 1973; "high exposure," September 1, 1973-December 31, 1974; and "post-fire," January 1, 1975-December 31, 1981.

RESULTS

During the high-exposure period, the exposed group had an increased prevalence of TLBW (OR=2.4; 90% CI: 1.6-3.6) and SGA (OR=1.9; 90% CI: 1.3-2.8) compared with the rest of Idaho. During the pre- and post-fire periods, the ORs for TLBW were 0.8 and 1.3, respectively, and for SGA, 1.0, and 1.3, respectively. During the high-exposure period, TMBW for the exposed group was 71 g lower than in the comparison group. The TMBW in the exposed group was 8 g lower in the pre-fire period and 26 g lower in the post-fire period than in the comparison group. The study found no increased risk for preterm birth in the exposed group.

CONCLUSIONS

Maternal exposures to airborne lead emissions appeared to be associated with increased risks for SGA, TLBW, and reduced TMBW.

Teratogen update: lead and pregnancy

This review focuses on the impacts of lead exposure on reproductive health and outcomes. High levels of paternal lead exposure (>40 microg/dl or >25 microg/dl for a period of years) appear to reduce fertility and to increase the risks of spontaneous abortion and reduced fetal growth (preterm delivery, low birth weight). Maternal blood lead levels of approximately 10 microg/dl have been linked to increased risks of pregnancy hypertension, spontaneous abortion, and reduced offspring neurobehavioral development. Somewhat higher maternal lead levels have been linked to reduced fetal growth. Some studies suggest a link between increased parental lead exposure and congenital malformations, although considerable uncertainty remains regarding the specific malformations and the dose-response relationships. Common methodological weaknesses of studies include potential exposure misclassifications due to the frequent unavailability of exposure biomarker measurements at biologically appropriate times and uncertainty regarding the best exposure biomarker(s) for the various outcomes. A special concern with regard to the pregnant woman is the possibility that a fetus might be exposed to lead mobilized from bone stores as a result of pregnancy-related metabolic changes, making fetal lead exposure the result of exposure to exogenous lead during pregnancy and exposure to endogenous lead accumulated by the woman prior to pregnancy. By reducing bone resorption, increased calcium intake during the second half of pregnancy might reduce the mobilization of lead from bone compartments, even at low blood lead levels. Subgroups of women who incurred substantial exposures to lead prior to pregnancy should be considered to be at increased risk.

Protecting children from environmental toxins

Lanphear and colleagues argue that the existing requirements in the US for toxicity testing and regulation of pesticides and industrial chemicals are inadequate to safeguard children

Preterm birth in relation to maternal organochlorine serum levels

PURPOSE

To evaluate the associations of serum levels of p,pacute;-DDE and two other persistent organochlorine pesticides, beta-HCH and HCB, in relation to preterm birth.

METHODS

During 1995 we performed a case-cohort study and 233 mothers were recruited at three large maternity hospitals in Mexico City. Serum levels were obtained shortly after delivery.

RESULTS

A non-significant increased risk of preterm birth in relation to serum p,p'-DDE levels was observed. There was also a suggestion of an increased risk of preterm birth among women in the highest tertile of beta-HCH (adjusted odds ratio 1.85, 95% CI = 0.94-3.66, p value for test of trend p = 0.08) compared with the lowest tertile. No association was found between HCB serum levels and preterm births.

CONCLUSIONS

These findings suggest that p,pacute;-DDE and other organochlorine pesticides may pose a risk to preterm birth in countries that continue to use such insecticides for malaria control.

Contaminant exposure among women of childbearing age who eat St. Lawrence River sport fish

Little information is available concerning the level of consumption and degree of contaminant exposure for North American women of childbearing age who eat sport fish. The authors reanalyzed a 1995-1996 study of Montreal-area (Canada) sport fishers. The authors focused on women sport fishers of childbearing age and male sport fishers who had spouses of childbearing age. The primary research involved an on-site questionnaire about fish consumption, with follow-up assessment of sport fishers estimated to have either the highest or lowest levels of fish-based contaminant exposure. Among the 1,654 interviewees were 100 women less than 45 yr of age who had eaten sport fish for an average of 11 yr; 45% ate fish less than once a month. From the follow-up subsample of high- and low-level consumers, the authors identified 17 women less than 45 yr of age and 25 males whose spouses who were less than 45 yr of age and who consumed similar quantities of sport fish. Among this group of 42, the high-exposure women differed from the low-exposure women with respect to their yearly consumption of freshwater fish, blood mercury levels (median = 6.4 vs. 1.4 microgram/l), and plasma polychlorinated biphenyl congener 99 (median = 10.5 vs. 5.9 microgram/kg plasma lipids). Few Montreal-area women of childbearing age consume local sport fish frequently or for extended periods. However, among the small proportion that consumes sport fish frequently or for extended periods, blood mercury concentrations approach levels of concern for fetal protection.