Review of recent Vietnamese studies on the carcinogenic and teratogenic effects of phenoxy herbicide exposure

Decreased serum testosterone levels associated with 17β-hydroxysteroid dehydrogenase activity in 7-year-old children from a dioxin-exposed area of Vietnam

Since 2008, we have conducted epidemiological cohort studies on the relationship between dioxin exposure and disruption with children in the area sprayed with defoliants during the Vietnam War. In a long-term survey of children through the age of five, we observed androgen disruption due to decreased dehydroepiandrosterone (DHEA) and testosterone levels. In this study of 7-year-old, we separately elucidated androgen disruption for boys and girls, and discussed with respect to hormone disruption with sex differences on the steroid hormone biosynthesis process. This follow-up was conducted with 96 mother-child pairs in Vietnam (hotspot area: 45, non-sprayed area: 51). We took a questionnaire, the physical measurement and assayed 7 steroid hormones in their serum by LC-MS/MS. We examined the relationship between the hormone levels in the serum and dioxin levels in the maternal breast milk. The results showed that the serum DHEA level in the 7-year-old children in the hotspot recovered to levels in the non-sprayed area. The testosterone level of 66.5 pg/mL for boys in the non-sprayed area was 1.5 times the girls level of 44.6 pg/mL, a male-dominant effect. The testosterone level in boys and girls from the hotspot were significantly lower than in the non-sprayed area with no sex difference. The 17β-hydroxysteroid dehydrogenase (17β-HSD) activity was significantly higher in boys than in the girls from the non-sprayed area, but was significantly lower in the hotspot boys than in the non-sprayed area boys. Both the testosterone level and 17β-HSD activity in the boys were inversely correlated with the TEQ total PCDD/Fs in the maternal breast milk. These results indicated that dioxin delayed the expression of the testosterone level and 17β-HSD activity with growth in the 7-year-old boys. The serum DHEA in the 7-year-old children recovered to the levels of the children in the non-sprayed area.

A relationship in adrenal androgen levels between mothers and their children from a dioxin-exposed region in Vietnam

Over the past decades, southern Vietnam has been burdened by dioxins from contaminated herbicides sprayed during the Vietnam War. In a previous study, we found that dioxin exposure decreased levels of salivary dehydroepiandrosterone (DHEA), an adrenal androgen, in 3-year-old children. In present study, to assess the relationship between adrenal hormones disruption in lactating mothers and in children, we compared mother-child pairs from dioxin- and nondioxin-contaminated regions. In 2010 and 2011, mother-child pairs from a dioxin hotspot region (n=37) and a non-contaminated region (n=47) were recruited and donated breast milk and serum samples for dioxin and steroid hormones determination. Mothers were 20-30years old and had given birth to their first child between 4 and 16weeks previously. One year later, saliva samples were collected from the children. Dioxin levels in breast milk were determined by gas chromatography/high-resolution mass spectrometry. Salivary DHEA, cortisol in children and androstenedione (A-dione), estradiol, cortisol, and DHEA in maternal serum were analyzed by liquid chromatography/tandem mass spectrometry. Concentrations of dioxin congeners in the hotspot region were 2- to 5-fold higher than in samples from the non-contaminated region. Salivary DHEA levels in children and serum A-dione levels in mothers were significantly higher in the hotspot region; no difference was found in the levels of other hormones. Moreover, there was a significant positive correlation between the elevated hormone levels in mothers and children (r=0.62, p<0.001). Several dioxin congeners exhibited strong significant dose-response relationships with salivary DHEA and serum A-dione levels. Our findings suggest that dioxin disrupts adrenal androgens in mothers and breastfeeding children through the same mechanism.

Pre- and post-conception pesticide exposure and the risk of birth defects in an Ontario farm population

The use of pesticides has enhanced the health and economies of nations around the world by improving crop production. However, pesticides may pose health risks, particularly to the fetus and young children. In a secondary analysis of the Ontario Farm Family Health Study, we explored the relationship between birth defects and parental pesticide exposure during the 3 months prior to conception and the first trimester of pregnancy. A total of 3412 pregnancies were included in the study. Logistic regression fit by maximum likelihood was used in the analysis. The results showed that pre-conception exposure to both cyanazine (odds ratio=4.99, 95% confidence interval: 1.63-15.27) and dicamba (OR=2.42, 95% CI: 1.06-5.53) were associated with increased risk of birth defects in male offspring. Nevertheless, given the self-reported nature of the exposure and outcomes in this study, the present findings should be considered primarily as hypothesis generating, requiring verification in subsequent investigations.

The impact of environmental pollution on congenital anomalies

Major congenital anomalies are diagnosed in 2-4% of births. In this paper we review epidemiological studies that have specifically looked at congenital anomalies as a possible outcome of community exposure to chemical exposures associated with environmental pollution. These include studies of drinking water contaminants (heavy metals and nitrates, chlorinated and aromatic solvents, and chlorination by-products), residence near waste disposal sites and contaminated land, pesticide exposure in agricultural areas, air pollution and industrial pollution sources, food contamination, and disasters involving accidental, negligent or deliberate chemical releases of great magnitude. We conclude that there are relatively few environmental pollution exposures for which we can draw strong conclusions about the potential to cause congenital anomalies and, if so, the chemical constituents implicated, to provide an evidence base for public health and clinical practice. A precautionary approach should be adopted at both community and individual level. In order to prevent congenital anomalies, one must reduce exposure to potential teratogens before pregnancy is recognized (i.e. preconceptionally and in the first few weeks of pregnancy). It is a challenge to develop effective strategies for preconceptional care within the primary care framework. Prenatal service providers and counsellors need to be aware of the uncertainties regarding environmental pollution when addressing parental concerns.

Open chemical combustions resulting in a local increased incidence of orofacial clefts

HYPOTHESIS

The open chemical combustions in Zeeburg, Amsterdam, The Netherlands, during the years 1961 up to and including 1969, resulted in a local increased incidence of orofacial clefts during this period.

STUDY

A retrospective observational epidemiological study was performed, comparing the trend of the incidence of non-syndromal orofacial clefts during the sixties, for the Zeeburg maternity with that of the Wilhelmina Gasthuis. Both clinics were situated in Amsterdam, but varying in distance and compass direction from the incineration works. Thereafter, the addresses of the mothers giving birth to infants with orofacial clefts were plotted on a map of Amsterdam.

RESULTS

Of the 8803 children born in the Zeeburg clinic during this period, 21 had a non-syndromal orofacial cleft, producing an average incidence of 2.4 per 1000 births. For the years 1963 through 1965 the incidence rose dramatically to peak at 7.1 per 1000, before plateauing at an average incidence of 1.68 per 1000 births, still 155% higher than in the Wilhelmina clinic (average incidence of 0.66 per 1000 during the years 1966 through 1969). During the 10 year period the Wilhelmina clinic exhibited no such rise. The incidence of non-syndromal orofacial clefts at the Wilhelmina clinic at no time exceeded 2.3 per 1000 births during the 10 year period. The addresses of the mothers of the Zeeburg clefts were grouped primarily to the northwest (and a smaller group to the west) of the incineration works.

CONCLUSION

A relation between the open incineration of the chemicals and a local increased incidence of orofacial clefts seems very likely.

Pesticide exposures and fetal death: a review of the epidemiologic literature

Despite considerable concern regarding the effects on reproductive outcome of exposures to pesticides, convincing evidence for the developmental toxicity of occupational and environmental pesticide exposure in humans is lacking. In this comprehensive review of the English language epidemiologic literature, we summarize studies that have examined potential associations between fetal deaths (both spontaneous abortions and stillbirths) and specific pesticides, as well as maternal and paternal employment in occupations with potential for exposure. While many of the epidemiologic studies to date suffer from methodologic problems, the data are suggestive of increased risks of fetal deaths associated with pesticides in general and maternal employment in the agricultural industry. There is a clear need for epidemiologic research that focuses on specific pesticide products or chemical families, with improved exposure assessment. The potential role of solvents in developmental toxicity associated with pesticide use by both males and females should also be considered.

Occupational hazards for the male reproductive system

The etiology of male infertilities is largely undetermined, and our knowledge of exogenous factors affecting the male reproductive system is still limited. In particular, the role of specific environmental and occupational factors is incompletely elucidated. Various occupational (physical and chemical) agents have been shown to affect male reproductive functions in animals, but large differences in reproductive function and/or xenobiotic handling between species limit extrapolation to humans. When available, human data are often conflicting and, except in a few instances, usually refer to broad and heterogenous occupational categories or to groups of agents (e.g., solvents). It is often difficult to elucidate the role of a single agent because occupational exposure conditions are often complex and various confounding factors related to lifestyle (smoking, alcohol, and diet) or socioeconomic state may also affect sperm quality, fertility, or pregnancy outcomes. The objective of this work is to summarize the main epidemiological and, where relevant, experimental findings pertaining to agents (physical and chemical) encountered in the occupational environment that might affect the male reproductive system (sperm count, motility and morphology, libido, and fertility) and/or related pregnancy outcomes (spontaneous abortion, stillbirth, low birth weight, and birth defects and childhood malignancy in offspring). Some methodological issues related to research on the reproductive effects of toxicants are also discussed briefly.

Review of epidemiologic studies of paternal occupational exposure and spontaneous abortion

The question of whether paternal exposures influence risk of spontaneous abortion is of great public interest, with the possibility supported by laboratory investigations. Thirty-nine studies of male occupational exposure and risk of spontaneous abortion were examined, with the methods and results tabulated. Many of those reports were limited by exposure data based on maternal report of the father's job title or by potentially inaccurate paternal reports of spontaneous abortion, though the quality of more recent studies is markedly enhanced. Mercury has been implicated most strongly based on recent studies that included quantitative exposure estimates; a number of studies showing associations for exposure to anesthetic gases. Suggestive associations have also been found inconsistently for exposure to lead, rubber manufacturing, selected solvents, and some pesticides. Further study is encouraged, but with more intensive effort to measure accurately both spontaneous abortion and occupational exposures.

Vietnamese infant and childhood mortality in relation to the Vietnam War

OBJECTIVES

There is obvious potential for war to adversely affect infant and childhood mortality through direct trauma and disruption of the societal infrastructure. This study examined trends in Vietnam through the period of the war.

METHODS

The 1988 Vietnam Demographic and Health Survey collected data on reproductive history and family planning from 4172 women aged 15 through 49 years in 12 selected provinces of Vietnam. The 13,137 births and 737 deaths to children younger than age 6 reported by the respondents were analyzed.

RESULTS

For the country as a whole, infant and childhood mortality dropped by 30% to 80% from the prewar period to the wartime period and was stable thereafter. In provinces in which the war was most intense, mortality did not decline from the prewar period to the wartime period but declined after the war, consistent with an adverse effect during the wartime period.

CONCLUSIONS

The data are limited by assignment of birth location on the basis of mother's current residence and by inadequate information on areas of war activity. Nonetheless, the data do not indicate a widespread, sizable adverse effect of the war on national infant and childhood mortality in Vietnam but suggest detrimental effects in selected provinces.

Paternal military service in Vietnam and the risk of late adverse pregnancy outcomes

To investigate the relationship between paternal military service in Vietnam and the risk of late adverse pregnancy outcomes, we conducted a case-control study of women who delivered infants from August 1977 until March 1980 at Boston Hospital for Women. Paternal military service history among 857 congenital anomaly cases, 61 stillbirth cases, and 48 neonatal death cases were compared with that of 998 normal controls. Military service veterans were identified by crossmatching identifying information from obstetric records with state and national military records. After controlling for confounding variables, we found that the Vietnam veterans' relative risk of fathering an infant with one or more major malformations was 1.7 (95% CI = 0.8, 3.5) compared to non-Vietnam veterans. The increased risk was present in several organ systems and did not seem to be related to a particular type of defect. No associations or highly unstable associations were found between paternal military service in Vietnam and the occurrence of congenital anomalies overall, minor malformations, normal variants, stillbirths, and neonatal deaths. These findings should be viewed with caution since maternal and delivery characteristics appear to have contributed to the etiology of several of the major malformations among the Vietnam veterans' children.

Dioxins and furans in the mother and possible effects on the fetus and newborn breast-fed baby

Due to pollution of the environment with PCBs, dioxins and furans these highly poisonous chemicals have accumulated in the adipose tissue of human beings. In breast milk of 14 mothers concentrations of dioxins and furans were found in milk fat, close to or in the range of the concentrations necessary to induce enzymes in "in vitro" rat liver cells (80-132 ppt). The hypothesis is that the above mentioned chemicals can be responsible for a vitamin K deficiency in the babies resulting in a bleeding analogous with phenobarbital. Both the pure TCDD content in milk fat and the content of dioxins and furans expressed as toxic equivalents (Nordic model) were higher in milk given to babies that presented a bleeding (4 out of 14). However, the sample size is too small for statistical analysis. No relation with age, parity, overweight, fish eating or smoking of the mother and dioxin content of her breast milk was seen in our small sample size.

Pesticides and cancer risks in agriculture

The work environment in agriculture is complex, with many potentially hazardous exposures, but the overall mortality from cancer and other causes is rather low among farmers. However, several studies have consistently indicated an excess of certain cancer forms. Lymphomas, leukemias, multiple myeloma and also malignancies of connective tissue attract special interest, as being possibly associated with the use of pesticides. Phenoxy acid herbicides may play an etiological role, especially for non-Hodgkin's lymphoma, whereas the findings are more ambiguous for Hodgkin's disease and soft-tissue sarcoma, perhaps indicating an interaction with co-factors. The issue has been controversial for many years, however, and one of its aspects involves the use of phenoxy acids in the Vietnam war. Furthermore, DDT has been associated with lung cancer in mixed exposure situations, and with chronic lymphatic leukemia. Arsenical pesticides may have caused skin cancer in vine-growers. Further studies, especially of specific user groups and producers, may avoid the complex exposure situation in agriculture.