Blood lead levels in children in south central Los Angeles

Pathways and sources of lead exposure: Michigan Children's Lead Determination (the MI CHILD study)

There has been little research on childhood lead exposure pathways since the 1990s. New data from Michigan in 2017-2021 for 429 children in 345 homes included lead in blood, paint, dust, soil, water, and other housing, demographic, and behavioral metrics. Fifty-three percent of these children had blood lead (BPb) ≥5 μg/dL. A repeated measures pathway model that accounted for multiple children in the same home was constructed using weighted least squares mean estimation and included variance-covariance model multiple imputation. Results showed that children's BPb was directly predicted by lead in settled floor house dust, child's age, season, and mouthing behavior and indirectly predicted by window sill and trough dust lead (DPb), bare soil lead (SPb), proportion of floors with carpets, and exterior building deteriorations. Paint lead (PPb) was also an indirect predictor of BPb through the soil and settled dust pathways. Water lead (WPb), water consumption and other lead sources/pathways were not significant predictors of BPb in this cohort. Although risk factors for individual children are highly variable and worthy of investigation to pinpoint their exposures, this study shows that the main direct and indirect pathways of lead exposure for most children in older housing remain paint and the contaminated dust and soil it generates. Pathway analyses in other jurisdictions using current data should be performed to confirm these results. This study suggests both DPb and BPb in high-risk homes may have declined since the 1990s and that lead in dust, soil, and paint all should be measured to predict risk and target remediation. Because most homes still have not been assessed for lead hazards and remediated, too many children remain at needless risk.

Use of Radioisotope Ratios of Lead for the Identification of Historical Sources of Soil Lead Contamination in Santa Ana, California

Lead (Pb) is an environmental neurotoxicant that has been associated with a wide range of adverse health conditions, and which originates from both anthropogenic and natural sources. In California, the city of Santa Ana represents an urban environment where elevated soil lead levels have been recently reported across many disadvantaged communities. In this study, we pursued a community-engaged research approach through which trained “citizen scientists” from the surrounding Santa Ana community volunteered to collect soil samples for heavy metal testing, a subset of which (n = 129) were subjected to Pb isotopic analysis in order to help determine whether contamination could be traced to specific and/or anthropogenic sources. Results showed the average 206Pb/204Pb ratio in shallow soil samples to be lower on average than deep samples, consistent with shallow samples being more likely to have experienced historical anthropogenic contamination. An analysis of soil Pb enrichment factors (EFs) demonstrated a strong positive correlation with lead concentrations, reinforcing the likelihood of elevated lead levels being due to anthropogenic activity, while EF values plotted against 206Pb/204Pb pointed to traffic-related emissions as a likely source. 206Pb/204Pb ratios for samples collected near historical urban areas were lower than the averages for samples collected elsewhere, and plots of 206Pb/204Pb against 206Pb/207 showed historical areas to exhibit very similar patterns to those of shallow samples, again suggesting lead contamination to be anthropogenic in origin, and likely from vehicle emissions. This study lends added weight to the need for health officials and elected representatives to respond to community concerns and the need for soil remediation to equitably protect the public.

Risk assessment of soil heavy metal contamination at the census tract level in the city of Santa Ana, CA: implications for health and environmental justice

(1) Background: exposure to heavy metals is associated with adverse health effects and disproportionately impacts low-income communities and communities of color. We carried out a community-based participatory research study to examine the distribution of heavy metal concentrations in the soil and social vulnerabilities to soil heavy metal exposures across Census tracts in Santa Ana, CA. (2) Methods: soil samples (n = 1528) of eight heavy metals including lead (Pb), arsenic (As), manganese (Mn), chromium (Cr), nickel (Ni), copper (Cu), cadmium (Cd), and zinc (Zn) were collected in 2018 across Santa Ana, CA, at a high spatial resolution and analyzed using XRF analysis. Metal concentrations were mapped out and American Community Survey data was utilized to assess metals throughout Census tracts in terms of social and economic variables. Risk assessment was conducted to evaluate carcinogenic and non-carcinogenic risk. (3) Results: concentrations of soil metals varied according to landuse type and socioeconomic factors. Census tracts where the median household income was under $50 000 had 390%, 92.9%, 56.6%, and 54.3% higher Pb, Zn, Cd, and As concentrations compared to high-income counterparts. All Census tracts in Santa Ana showed hazard index >1, implying the potential for non-carcinogenic health effects, and nearly all Census tracts showed a cancer risk above 10-4, implying a greater than acceptable risk. Risk was predominantly driven by childhood exposure. (4) Conclusions: findings inform initiatives related to environmental justice and highlight subpopulations at elevated risk of heavy metal exposure, in turn underscoring the need for community-driven recommendations for policies and other actions to remediate soil contamination and protect the health of residents.

Social and spatial distribution of soil lead concentrations in the City of Santa Ana, California: Implications for health inequities

BACKGROUND

Lead (Pb) exposure is a problem that disproportionately impacts low-income communities and communities of color. We applied a community-based participatory research approach to assess the distribution of soil Pb concentrations and related social vulnerabilities across Census tracts in Santa Ana, CA.

METHODS

Soil Pb samples (n = 1528) were collected by the ¡Plo-NO! Santa Ana! Lead-Free Santa Ana! partnership in 2018 across Santa Ana, CA, at a high spatial resolution and measured using XRF analysis. Pb concentrations were mapped and spatial interpolation was conducted to generate a continuous smoothed map of soil Pb concentrations across the city. American Community Survey data was used to examine Pb across Census tracts based on social and economic factors, and to allow for the development of a Cumulative Risk Index to identify areas at high risk of health impacts.

RESULTS

Soil Pb concentrations varied by landuse type and socioeconomic factors. Census tracts with a median household income below $50,000 had over five times higher soil Pb concentrations than high-income Census tracts. Soil samples collected in tertiles with the highest percent children, residents without health insurance, renter-occupied housing units, and lowest percent college educated residents had 90.0%, 96.1%, 75.2%, and 87.0% higher Pb concentrations on average, respectively, compared to their counterparts. Overall, 52.7% of residential samples had Pb concentrations in excess of the 80 ppm California EPA recommendation, and 11 Census tracts were characterized as high risk according to our Cumulative Risk Index.

DISCUSSION

This study underscores the need for precautionary measures relating to disturbances of the soil, particularly for areas where children play outside, given children's higher absorption of lead. It also informs environmental justice initiatives and identifies vulnerable subpopulations at greater risk of Pb exposure, thus warranting community-driven recommendations for policies and initiatives to remediate soil Pb and protect public health and health equity.

The State of Public Health Lead Policies: Implications for Urban Health Inequities and Recommendations for Health Equity

Although lead has been removed from paint and gasoline sold in the U.S., lead exposures persist, with communities of color and residents in urban and low-income areas at greatest risk for exposure. The persistence of and inequities in lead exposures raise questions about the scope and implementation of policies that address lead as a public health concern. To understand the multi-level nature of lead policies, this paper and case study reviews lead policies at the national level, for the state of California, and for Santa Ana, CA, a dense urban city in Southern California. Through a community-academic partnership process, this analysis examines lead exposure pathways represented, the level of intervention (e.g., prevention, remediation), and whether policies address health inequities. Results indicate that most national and state policies focus on establishing hazardous lead exposure levels in settings and consumer products, disclosing lead hazards, and remediating lead paint. Several policies focus on mitigating exposures rather than primary prevention. The persistence of lead exposures indicates the need to identify sustainable solutions to prevent lead exposures in the first place. We close with recommendations to reduce lead exposures across the life course, consider multiple lead exposure pathways, and reduce and eliminate health inequities related to lead.

Children's Blood Lead Seasonality in Flint, Michigan (USA), and Soil-Sourced Lead Hazard Risks

In Flint; MI; USA; a public health crisis resulted from the switching of the water supply from Lake Huron to a more corrosive source from the Flint River in April 2014; which caused lead to leach from water lines. Between 2010 and 2015; Flint area children’s average blood lead patterns display consistent peaks in the third quarter of the year. The third quarter blood lead peaks displayed a declining trend between 2010 and 2013; then rose abruptly between the third quarters of 2013 from 3.6% blood lead levels ≥5 µg/dL to a peak of about 7% in the third quarter of 2014; an increase of approximately 50%. The percentage of blood lead level ≥5 µg/dL in the first quarter of 2015 then dropped to 2.3%; which was the same percentage as the first quarter of 2014 (prior to the Flint River water source change). The Flint quarterly blood lead level peak then rose to about 6% blood lead levels ≥ 5 µg/dL in the third quarter of 2015; and then declined to about 2.5% in the fourth quarter of 2015. Soil lead data collected by Edible Flint food collaborative reveal generally higher soil lead values in the metropolitan center for Flint; with lower values in the outskirts of the city. The questions that are not being asked is why did children’s blood lead levels display a seasonal blood lead pattern before the introduction of the new water supply in Flint; and what are the implications of these seasonal blood lead patterns? Based upon previous findings in Detroit and other North American cities we infer that resuspension to the air of lead in the form of dust from lead contaminated soils in Flint appears to be a persistent contribution to lead exposure of Flint children even before the change in the water supply from Lake Huron to the Flint River.

Role of NAD(+), Oxidative Stress, and Tryptophan Metabolism in Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a pervasive neuro-developmental disorder characterized by impaired social interaction, reduced/absent verbal and non-verbal communication, and repetitive behavior during early childhood. The etiology of this developmental disorder is poorly understood, and no biomarkers have been identified. Identification of novel biochemical markers related to autism would be advantageous for earlier clinical diagnosis and intervention. Studies suggest that oxidative stress-induced mechanisms and reduced antioxidant defense, mitochondrial dysfunction, and impaired energy metabolism (NAD(+), NADH, ATP, pyruvate, and lactate), are major causes of ASD. This review provides renewed insight regarding current autism research related to oxidative stress, mitochondrial dysfunction, and altered tryptophan metabolism in ASD.

Effects of HUD-supported lead hazard control interventions in housing on children's blood lead

The Evaluation of the US Department of Housing and Urban Development Lead-Based Paint Hazard Control Grant Program studied the effectiveness of the housing intervention performed in reducing the blood lead of children at four post-intervention times (6-months, 1-year, 2-years, and 3-years). A repeat measures analysis showed that blood lead levels declined up to three-years post-intervention. The results at each successive collection time were significantly lower than at the previous post-intervention time except for the difference between the levels at two and three years. At two-years post-intervention, geometric mean blood lead levels were approximately 37% lower than at pre-intervention. Children with pre-intervention blood lead levels as low as 10 μg/dL experienced substantial declines in blood lead levels. Previous studies have found substantial improvements only if a child's pre-intervention blood lead level was above 20 μg/dL. Individual interior lead hazard control treatments as grouped by Interior Strategy were not a significant predictor of post-intervention blood lead levels. However, children living in dwellings where exterior lead hazard control interventions were done had lower blood lead levels at one-year post-intervention than those living in dwellings without the exterior interventions (all other factors being equal), but those differences were only significant when the mean exterior paint lead loading at pre-intervention was about the 90th percentile (7.0mg/cm(2)). This observation suggests that exterior lead hazard control can be an important component of a lead hazard control plan. Children who were six to eleven months of age at pre-intervention had a significant increase in blood lead at one-year post-intervention, probably due to other exposures.

Measurement of selected ions related to oxidative stress and energy metabolism in Saudi autistic children

OBJECTIVES

Autism is a developmental disorder characterized by social and emotional deficits, language impairments and stereotyped behaviors that manifest in early postnatal life. This study aims to clarify the role of selected ions related to energy metabolism as a consequence of oxidative stress in the deterioration accompanied autism.

MATERIALS AND METHODS

Malonaldehyde as measure of lipid peroxidation, Na(+)/K(+) ion pump (ATPase), together with the concentrations of Na(+), K(+), Mg(2+), Ca(2+) and Pb(2+) were determined in plasma of 30 Saudi autistic patients and compared to 30 age-matching control samples.

RESULTS

The obtained data recorded that Saudi autistic patients have a remarkable higher activities of Na(+)/K(+) ATPase and high levels of lipid peroxidation compared to control. In addition, they have significantly elevated levels of K(+) and Pb(2+) while Ca(2+) recorded a significantly lower level compared to age-matching control subjects. On the other hand both Mg(2+) and Na(+) were non-significantly changed in autistic patients.

CONCLUSION

Alteration of the selected measured ions confirms that oxidative stress and defective mitochondrial energy production could represent the primary causative factor in the pathogenesis of autism.

Improved participation for blood lead screening with in-home phlebotomy

Both nationally and within the State of California, it is unlikely that those children most susceptible to lead exposure are adequately screened for blood lead levels. New and creative approaches are necessary to reach these individuals. In-home phlebotomy was employed to test blood lead levels of 128 San Diego households containing Latino children aged 12-71 months. As part of a lead exposure study, these households were randomly selected from 12 census tracts in the downtown area during February-July, 2006. By employing a bicultural/bilingual phlebotomist, the participation rate for in-home phlebotomy was 89% among enrolled study participants. This rate is substantially higher than estimates for customary testing of similar underserved groups through physicians, has the advantage of reaching individuals without medical insurance, and contrasts favorably ($45 per individual test) with typical office visit costs. Culturally appropriate in-home phlebotomy may be a useful method for medical screening to meet the needs of underserved communities. Editors' Strategic Implications: The authors provide an excellent example of the importance of bringing prevention services to clients, literally in terms of the home visitation format but also with respect to the comfort level that may come from interacting with a bicultural and bilingual professional.

Hair-Pb longitudinal profiles and blood-Pb in the population of young Slovenian males

Hair-Pb longitudinal profiles of 25 mm hair length were measured in a population of Slovenian men (aged 18-25 years) using "tape sandwich" solid sampling electrothermal atomic absorption spectrometry (SS-ETAAS). From these data two parameters related to Pb exposure were deduced. Hair-Pb proximal (H-Pbprox.) denotes the Pb content of the proximal 3mm hair segment, while Hair-Pb average (H-Pbaver.) denotes the average Pb content of a 25 mm hair length. The former were found to be on average at least a factor of 2 lower than the H-Pbaver. values that are normally reported in the literature for hairs of 20-50 mm length. Hair-Pb gradient (H-Pbgrad.) defined as the difference in Pb content between the distal (25 mm) and the proximal (3 mm) hair segments divided by the hair length was found to be highly correlated to the level of air Pb pollution (R=0.9931; P<0.001; n=5), while association between H-Pbprox. and air-Pb was not significant (R=0.5765; P>0.05; n=5). Simultaneously, lead in whole blood (B-Pb) was determined by ETAAS as another parameter of Pb exposure. The frequency distribution of log B-Pb values followed a symmetrical Gaussian shape with a median value of 35 microg Pb/L. Log H-Pbprox. frequency distribution, on the contrary, showed a Poissonian shape. Transformation of the data revealed the existence of four homogeneous groups of males with different median H-Pbprox. values (40, 86, 326 and 2500 ng/g). The major proportion of the Slovenian male population ( approximately 70%) has H-Pbprox. contents between 60 and 600 ng/g. A weak but statistically significant association was found between logs H-Pbprox. and B-Pb (R=0.3957; P<0.05; n=247) but when only those subjects were retained whose both parameters were determined with reasonable accuracy and were either above or below the predetermined value (B-Pb=50 microg/L; H-Pbprox.=450 ng/g), substantial improvement in the strength of correlation was observed (R=0.7049; P<0.01; n=84). The poor strength of association between these parameters was attributed to the large variation in Pb intake and different kinetics of Pb appearance in hair and blood. This statement is consistent with reports dealing with the relationship between H-Pb and B-Pb found in the literature.

Distribution of lead in urban roadway grit and its association with elevated steel structures

In an effort to determine the source of exterior lead contamination, we investigated the concentration of lead in roadway grit along major thoroughfares in New York City and in certain areas under elevated steel structures supporting elevated rails. Such structures represent only one source of lead in roadway grit. While data revealed that the median lead concentration in roadway grit did not exceed the standard for a lead hazard in bare residential soil in any borough, the limit of 400 microg/g was exceeded 22%, 18%, 10.5%, and 7.7% of the time in Manhattan, Brooklyn, The Bronx, and Queens, respectively. The second part of the study revealed the presence of high concentrations of lead in roadway grit directly under elevated steel structures. The differences in the concentration of lead in roadway grit under steel structures in comparison to areas in NYC not near elevated rails was statistically significant. Of the eight sites studied from 225 total samples, the median roadway grit lead level was 340 ppm, while the level under steel structures was 1480 ppm. Preliminary efforts to determine particle size distribution revealed that 84% of the particles were in the range of 125-500 microm, but the highest concentration of lead was in the smallest fraction analyzed (<63 microm). Lead contamination of roadway grit from restoration of elevated painted steel structures is a public health problem as these lead particulates get re-suspended in the ambient environment and are wafted and tracked into residences.

Seasonality and children's blood lead levels: developing a predictive model using climatic variables and blood lead data from Indianapolis, Indiana, Syracuse, New York, and New Orleans, Louisiana (USA)

On a community basis, urban soil contains a potentially large reservoir of accumulated lead. This study was undertaken to explore the temporal relationship between pediatric blood lead (BPb), weather, soil moisture, and dust in Indianapolis, Indiana; Syracuse, New York; and New Orleans, Louisiana. The Indianapolis, Syracuse, and New Orleans pediatric BPb data were obtained from databases of 15,969, 14,467, and 2,295 screenings, respectively, collected between December 1999 and November 2002, January 1994 and March 1998, and January 1998 and May 2003, respectively. These average monthly child BPb levels were regressed against several independent variables: average monthly soil moisture, particulate matter < 10 microm in diameter (PM10), wind speed, and temperature. Of temporal variation in urban children's BPb, 87% in Indianapolis (R2 = 0.87, p = 0.0004), 61% in Syracuse (R2 = 0.61, p = 0.0012), and 59% in New Orleans (R2 = 0.59, p = 0.0000078) are explained by these variables. A conceptual model of urban Pb poisoning is suggested: When temperature is high and evapotranspiration maximized, soil moisture decreases and soil dust is deposited. Under these combined weather conditions, Pb-enriched PM10 dust disperses in the urban environment and causes elevated Pb dust loading. Thus, seasonal variation of children's Pb exposure is probably caused by inhalation and ingestion of Pb brought about by the effect of weather on soils and the resulting fluctuation in Pb loading.

Blood lead secular trend in a cohort of children in Mexico City (1987-2002)

We determined the secular trend in blood lead levels in a cohort of 321 children born in Mexico City between 1987 and 1992. Blood lead level was measured every 6 months during a 10-year period. We modeled the effect of yearly air lead concentration nested within the calendar year in which the child was born, family use of lead-glazed pottery, socioeconomic status, year in which the child was born, age of the child at the time of blood lead measurement, place of residence, and an indicator variable for subjects with complete or incomplete blood lead values. The yearly mean of air lead of the Valley of Mexico decreased from its highest level of 2.80 microg/m3 in 1987 to 0.07 microg/m3 in 2002. The contribution of air lead to blood lead according to year of birth was strongest for subjects born in 1987 and fell to nearly zero for children born in 1992. The geometric mean of the entire cohort rose from 8.4 microg/dL in the first year of life to 10.1 microg/dL in the second and decreased thereafter until it reached 6.4 microg/dL at 10 years of age. Children of families who used lead-glazed ceramics had blood lead levels 18.5% higher than did children of nonusing families. Children who belonged to the lowest socioeconomic levels had blood lead levels 32.2% higher than did those of highest socioeconomic levels. Children who lived in the northeast part of the city had blood lead levels 10.9% higher compared with those who lived in the southwest.

Seasonality and trend in blood lead levels of New York State children

Background

Environmental exposure to lead remains a significant health problem for children. The costs of lead exposure in children are estimated to be considerably more than other childhood diseases of environmental origin. While long-term trends in blood lead levels (BLLs) among children are declining, seasonal variation persists. Cross-sectional studies have found a peak in summer months. Part of this variation may be due to increased exposure to lead paint on window sills and through increased contact with soils containing lead during the summer. The current study represents the largest published population-based study on seasonality and trends in the BLLs of children to date. In addition, the results offer a comparison of recent data on seasonality of BLLs in New York State children, to studies conducted over the past three decades.

Methods

262,687 New York State children born between 1994 and 1997 were screened for blood lead within 2 weeks of their first or second birthdays. Time series analyses of blood lead data from these children were conducted to study the seasonality and trends of BLLs.

Results

Children's blood lead values showed a distinct seasonal cycle on top of a long-term decreasing trend. The geometric mean BLL declined by about 24% for children born between 1994 and 1997. The prevalence of elevated BLLs in two-year-olds was almost twice that in one-year-olds over the time period. Nearly twice as many children had elevated BLLs in the late summer compared to late winter/early spring. In this and previous cross-sectional studies, the amount of seasonality as a proportion of the mean ranged between 15% and 30%.

Conclusion

Pediatricians should be aware of the seasonality of BLLs. For example, if a two-year-old receives a borderline result during the winter, it is possible that the levels would have been higher if he had been tested during the summer. However, physicians should continue to screen children at their normally scheduled well-child visits rather than delaying until summertime and possibly postponing the discovery of an elevated BLL. Age, season, and time trends still need to be considered in lead studies and result interpretation.

In utero exposure to lead and cord blood total IgE. Is there a connection?

BACKGROUND

Lead exposure and total immunoglobulin E (IgE) have been shown to be positively related in animals and humans even at lead levels below those recognized as toxic. In the last decades, exposure to lead has become more frequent in urban areas of industrialized as well as of developing countries where IgE-mediated allergy prevalence has also increased.

METHODS

We examined for the first time the relationship between in utero exposure to lead and cord blood total IgE in two samples of 137 and 237 mother-newborn pairs, respectively, recruited in Paris.

RESULTS

Cord blood IgE was positively related to hair lead level at birth, providing an integrated measure of long-term exposure in utero, in each cohort (Spearman's coefficient r = 0.32, P < 0.001 and r = 0.19, P < 0.01, respectively) and in the combined cohort (r = 0.21; P < 0.01). The relationship appeared to be more pronounced in newborns of nonallergic mothers (r = 0.24; P < 0.01) than in those of allergic mothers (r = 0.12). This could be due to the fact that familial history of allergy, the strongest determinant of IgE development, may overshadow the influence of lead on IgE in the offspring.

CONCLUSIONS

Our findings suggest a possible intervention of environmental exposure besides genetic factors in early life development of IgE production. Further studies are needed to confirm the finding.

Lead intervention and pediatric blood lead levels at hazardous waste sites

Lead intervention at Superfund sites typically seeks to reduce pediatric blood lead levels by disrupting the surface-to-hand-to-mouth pathway. This article presents the results of a survey of the publicly available literature on the effectiveness of lead intervention on pediatric blood lead levels at hazardous waste sites. The survey includes six hazardous waste sites located in Canada, Australia, and the United States at which intervention activities were conducted and pediatric blood lead levels were sampled both pre- and postintervention. Evaluation of the effectiveness of intervention on pediatric blood lead levels is often complicated due to confounding variables and statistical limitations. Nevertheless, the outcomes of the intervention studies reviewed in this report suggest that various approaches to the intervention of the dust ingestion pathway, alone or in combination, contributed to declines in blood lead levels in children living in areas heavily contaminated with lead.

Evaluation of a childhood lead questionnaire in predicting elevated blood lead levels in a rural community

The accuracy of a lead screening questionnaire in predicting elevated blood lead levels was examined in a pediatric practice in a rural part of New York state. A retrospective chart review was used to collect data on children ages 9 to 24 months who presented for well-child visits. Children with both questionnaire and lead level results available in the chart were included in the study (n = 171). The mean blood lead level among all children was 1.6 microg/dl (median = 2.0 microg/dl, range 0 to 24 microg/dl). Four children (2.3%) had elevated lead levels (greater than 10 microg/dl), with levels for two of these children being greater than 20 microg/dl. Although our lead screening questionnaire was expanded from the standard 1991 CDC questionnaire by the inclusion of six additional items, it was not especially useful in predicting elevated blood lead levels above 10 microg/dl. However, the questionnaire exhibited some utility in predicting marked elevations in blood lead levels (over 20 microg/dl). Although results in other geographic areas might differ, the lead questionnaire may have value by enhancing parents' awareness of potential lead hazards in their children's environment and may prove to be more useful in areas of high risk to lead exposure.

Sperm count and chromatin structure in men exposed to inorganic lead: lowest adverse effect levels

OBJECTIVES

To obtain knowledge on male reproductive toxicity of inorganic lead at current European exposure levels and to establish lowest adverse effect levels, if any.

METHODS

A cross sectional survey of the semen of 503 men employed by 10 companies was conducted in the United Kingdom, Italy, and Belgium. The mean blood lead concentration was 31.0 microg/dl (range 4.6-64.5) in 362 workers exposed to lead and 4.4 microg/dl (range below the detection limit of 19.8) in 141 reference workers. Semen volume and sperm concentration were determined in a fresh semen sample according to an agreed protocol subject to quality assurance. The sperm chromatin structure assay (SCSA) was performed at a centralised laboratory. Extraneous determinants including centre, period of sexual abstinence, and age were taken into account in the statistical analysis. If appropriate, possible thresholds were examined by iterative threshold slope linear regression.

RESULTS

The median sperm concentration was reduced by 49% in men with blood lead concentration above 50 microg/dl. There was no indication of a linear trend of lower sperm concentration with increasing blood lead values, but threshold slope least square regression identified a blood lead concentration of 44 microg/dl (beta=-0.037, F=4.35, p=0.038) as a likely threshold. Abnormal sperm chromatin structure was not related to blood lead concentration, but some indications of deterioration of sperm chromatin was found in men with the highest concentrations of lead within spermatozoa. Biological monitoring data did not indicate long term effects of lead on semen quantity or sperm chromatin.

CONCLUSION

Adverse effects of lead on sperm concentration and susceptibility to acid induced denaturation of sperm chromatin are unlikely at blood lead concentrations below 45 microg/dl. Effects of low level exposure to lead on other measures of testicular function cannot be ruled out.

Relationships between blood lead concentrations, intelligence, and academic achievement of Saudi Arabian schoolgirls

This cross-sectional study examined the association between blood lead levels and neuropsychological and behavioural problems of 533 schoolgirls (6-12 years of age) who attended public schools in Riyadh, Capital of Saudi Arabia. Regression models were used to determine the best predictors of Beery VMI Saudi-based standard scores, TONI Saudi-based scores and rank percentile. The mean blood lead level was 8.11 +/- 3.50 micrograms/dl in the range of 2.3 to 27.36 micrograms/dl. Significant negative associations were noted between blood lead levels and Beery VMI Saudi-based standard scores as well as rank percentile. Lead had no effect on TONI Saudi-based standard scores. Beery VMI Saudi-based standard scores, TONI Saudi-based standard scores and rank percentiles were inversely related to pupils with blood lead levels > 9 micrograms/dl. These findings attest an association between neuropsychological and behavioural impairment and lead exposure at blood lead levels in the range of 9.02 to 27.36 micrograms/dl. The results of this study should be seriously considered by public health authorities to give more attention to this pediatric health problem.

Seasonal variation in bone lead contribution to blood lead during pregnancy

Population blood lead level (PbB) often shows seasonal variation, frequently being higher in summer and lower in winter. As vitamin D metabolites also show seasonal variability, and the metabolites are associated with bone metabolism, some authors have posited a role for bone lead release in seasonal PbB changes. We made third trimester and postdelivery PbB measurements on 414 immigrant women (98% Latina) in Los Angeles. We measured in vivo tibia and calcaneus (heel) lead concentration postdelivery via K-shell X-ray fluorescence. We saw evidence of seasonal variation in prenatal PbB, but not postnatal PbB. PbB was highest in spring and lowest in autumn. Tibia lead concentration was associated with prenatal PbB, as reported before. The contribution of tibia lead to prenatal PbB varied seasonally, with the greatest contribution occurring in the winter quarter and the least in the summer quarter. The temporal pattern of bone lead contribution to PbB follows the seasonal alteration of insolation. There was no seasonal component in prenatal PbB associated with calcaneus lead, nor were there seasonal variations in either calcaneus or tibia lead contributions to postnatal PbB. Bone turnover in the third trimester of pregnancy may be higher in winter months than in summer months, resulting in greater fetal lead exposure in spring than at other times of the year.

Increase in vulnerability of middle-aged rat brain to lead by cerebral energy depletion

The neurotoxic effects of low-level lead (Pb) during senescence are increasing interests of importance. We investigated the effects of low-level Pb on the brain in a normal condition and a pathophysiological condition of energy shortage that is commonly found in age-related neurological diseases. Middle-aged rats (15 months old) were exposed to 200 mg/l Pb acetate in drinking water for 2 months and thereafter received bilateral intracerebroventricular injections of streptozotocin (STZ). After 1 month's additional exposure to the same level of Pb solution as before the rats were sacrificed. Blood and brain Pb levels were measured by graphite furnace atomic absorption spectrophotometry. Energy-rich phosphate levels in the brain were determined by high-performance liquid chromatography equipped with a UV detector. Astroglial activation and glucose-regulated protein (GRP)94 expression were examined immunohistochemically. Exposure to Pb increased the blood Pb level to 10.8 microg/dl and the brain Pb level to 0.052 microg/g. But a significant additional increase in the brain Pb level, to 0.101 microg/g, became obvious in rats treated with Pb + STZ. Both Pb and STZ induced perturbation in brain energy metabolism, but no further alteration in energy metabolite levels was found in rats treated with Pb + STZ. Astroglial activation and GRP94-positive astrocytes and neurons were found only in the brains of Pb + STZ-treated rats. These results suggest that exposure to low-level Pb can perturb brain energy metabolism and the brain becomes more vulnerable to Pb when it is under energy stress.

Blood lead secular trend in a cohort of children in Mexico City. II. 1990-1995

The authors determined the secular trend in blood lead levels in a cohort of 91 children born in Mexico City between 1987 and the beginning of 1993. The authors grouped children by calendar year in which they reached 36 mo of age (i.e., 1990-1995), and their blood lead levels were measured every 6 mo during a 66-mo period. The overall geometric mean blood lead level was 8.6 microg/dl (range = 1.0-61.0 microg/dl). A repeated measures analysis of variance revealed a significant downward linear trend in blood lead levels by year (p < .001)--from an estimated marginal geometric mean of 14.2 microg/dl in 1990 to 6.3 microg/dl in 1995. There was also a significant linear age effect (p < .001); blood lead levels generally fell during the 36th-66th mo. Family use of lead-glazed pottery significantly elevated blood lead levels (p = .006), and the effect magnified as age increased (Age x Pottery Interaction [p = .014]). Although the overall downward trend in blood lead levels during the time period described corresponded to a reduction in various sources of lead exposure, there was no alteration in production, distribution, or use of leaded pottery. Currently, use of lead-glazed ceramic pottery is one of the most profound sources of lead exposure in the Mexican population.

Maternal blood lead level during pregnancy in South Central Los Angeles

Twenty-five years of public health efforts produced a striking reduction in lead exposure; the blood lead average in the United States has decreased to less than 20% of levels measured in the 1970s. However, poor minority groups that live in large urban centers are still at high risk for elevated lead levels. In this study, our data showed that pregnant immigrants (n = 1,428) who live in South Central Los Angeles--one of the most economically depressed regions of California--have significantly higher (p < .0001) blood lead levels (geometric mean = 2.3 microg/dl [0.11 micromol/l]) than 504 pregnant nonimmigrants (geometric mean = 1.9 microg/dl [0.09 micromol/l]). The most important factors associated with lower blood lead levels in both groups were younger age; more-recent date of blood sampling (i.e., decreasing secular trend); and blood sampling in mid-autumn, instead of mid-spring (i.e., seasonal trend). Blood lead levels of immigrants were strongly dependent on time elapsed since immigration to the United States; each natural log increase in years of residence was associated with an approximately 19% decrease in blood lead levels. Although blood lead means for both groups were almost the same as the estimated national average, 25 of the 30 cases of elevated blood lead (i.e., > or = 10 microg/dl [0.48 micromol/l) occurred in the immigrant group. The odds ratio (95% confidence intervals within parentheses) for having elevated blood lead levels (a) was 9.3 (1.9, 45.8) if the immigrant engaged in pica; (b) was 3.8 (1.4, 10.5) if the immigrant had low dietary calcium intake during pregnancy; and (c) was .65 (.43, .98) for every natural log unit increase of years of residence in the United States. The control of pica and dietary calcium intake may offer a means of reducing lead exposure in immigrants.

Determinants of blood lead levels in Saudi Arabian schoolgirls

Blood lead levels were measured in 538 girls aged 6 to 12 years who attended primary public schools in Riyadh, Saudi Arabia. Of the 538 screened children, 24.4% had blood lead levels > or =10 microg/dL, the Centers for Disease Control's level of concern. Variation in the blood lead levels was investigated with respect to a number of risk factors. The main determinant of blood lead levels was the regional location of the school. Pupils who attended schools located in the Central region of Riyadh had significantly higher blood lead concentrations than did pupils who attended schools in the peripheral areas. This is most likely to be due to the heavy vehicular emissions in the Central region. Other variables such as low family income, grade, and application of kohl to the child's eyes and/or umbilicus at birth were also contributors to the blood lead levels. These observations emphasize the importance of health education programs to promote the reduction of lead exposure in the general population.