Our cohort of peripubertal boys in Chapaevsk, Russia, had high serum levels of dioxins and PCBs compared with other populations (Link et al. 2005
; Patterson et al. 2008
). Like other studies, we found that older age of the boy, longer breast-feeding duration, and consumption of local foods were associated with higher serum concentrations of dioxins and PCBs (Choi et al. 2006
; Hauser et al. 2005
; Link et al. 2005
). Residential proximity to and maternal employment at Khimprom, as well as maternal local gardening, were associated with higher serum dioxins and PCBs among the boys.
Studies of serum dioxin and PCB concentrations among children are limited, and we are unaware of data from other Russian children. The median serum total 2005 TEQs of the 8- to 9-year-old Chapaevsk boys was triple the geometric mean from the U.S. National Health and Nutrition Examination Survey for males 12–19 years of age (there were no data on children < 12 years of age) (Patterson et al. 2008
). Among this U.S. age group, PCDDs/PCDFs contributed 86% to the total TEQs compared with 63% of total TEQs in Chapaevsk boys, suggesting proportionately greater exposure to C-PCBs and M-PCBs among the boys in Chapaevsk. Similarly, serum total 1998 TEQs of the Chapaevsk children were almost triple the levels measured among German children (mean age, 10.2 years) during 2002–2003 (Link et al. 2005
). However, the contribution of PCDDs/PCDFs to the total 1998 TEQs was comparable between the German (49%) and Chapaevsk (46%) children.
The results of our study suggest that industrial contamination of the local environment may be an important source of exposure for the Chapaevsk boys. Boys who lived closest to the Khimprom plant had significantly higher serum dioxin and PCB concentrations, and environmental (soil, house dust) and human (breast milk, serum) samples from residential areas closest to Khimprom had higher dioxin and PCB levels (Sergeyev et al. 2007
). The finding of high serum PCBs was unexpected, because PCBs were not manufactured at Khimprom, although they may have been used at the plant. The summary measures based predominantly on PCBs were also higher among boys who had lived longer in Chapaevsk, even after adjustment for age, suggesting that the local environment and foods of Chapaevsk may be an important source of PCB exposure. The boys whose mothers reported having local gardens had higher serum dioxin and PCB levels, even after adjustment for local food consumption. This suggests the possibility that mothers exposed to contaminated garden soil may have transferred these exposures to their sons by breast-feeding or that their sons were involved in gardening or playing in the garden area, thereby increasing their exposure to these compounds through contact with the contaminated garden soil.
Dietary consumption of local eggs, meats, poultry, dairy, and fish were significantly associated with higher serum dioxins and PCBs among the Chapaevsk boys. In other studies, elevated blood dioxin and PCB concentrations have been linked to local food consumption in areas with environmental exposures to these compounds (Choi et al. 2006
; Hauser et al. 2005
; Schecter et al. 2003
). Research in Chapaevsk suggests that local eggs and fish have significantly higher concentrations of dioxins and PCBs compared with other regions in Russia (Sergeyev et al. 2007
; Shelepchikov et al. 2006
). Although the mechanism for egg contamination is unknown, it may be either the result of chickens feeding in contaminated soil or eating contaminated feed, as suggested in other studies (Hayward and Bolger 2005
; Schoeters and Hoogenboom 2006
). Local nonpoultry meat and poultry consumption were also associated with higher serum dioxin and PCB concentrations among the boys. Although prior studies have found that meats contribute to dioxin and PCB exposure (Charnley and Doull 2005
; Fernandez et al. 2004
), < 10% of the Chapaevsk boys ate meats from local sources; thus, this association should be cautiously interpreted. The associations between the consumption of local nonpoultry meat, poultry, their products such as eggs and dairy, and fish with higher serum dioxins and PCBs suggest that both local animals and their products may be important sources of these compounds. Animal products such as eggs, milk, and cheese are important sources of protein in Chapaevsk. This is enhanced by the local population having access to animal products from local farms; nearly half of the study participants reported eating local dairy products, and 16% ate local eggs. Additionally, most families in this community consume local fruits and vegetables, and the boys who consumed the most had significantly higher serum total TEQ concentrations. The observation that local foods were associated with higher serum dioxin and PCB concentrations presents a dilemma for this community, where the consumption of local foods is both a common practice and an important source of protein, fruits, and vegetables.
Boys whose mothers had been employed in the Khimprom plant had higher serum dioxin and PCB levels, suggesting these mothers may have had occupational exposure with increased body burdens and transferred more of these compounds to their sons via breast-feeding. Consistent with this finding, some of the children of workers in a phenoxy herbicide chemical plant in Ufa, Russia, had elevated serum TCDD concentrations (Ryan and Schecter 2000
). However, because only 6% of the mothers were ever employed at the Khimprom plant, the association with higher serum dioxin and PCB concentrations among their sons should be interpreted cautiously.
In our study, occupation of the mothers and local gardening were associated with higher serum dioxin and PCBs levels among the sons. Although we carefully assessed and controlled for potential confounders of these associations, such as household income, parental education, residence, and dietary consumption of local foods, this adjustment may not have been sufficient.
Boys with higher BMIs had lower serum dioxin and PCB concentrations. Similarly, a cross-sectional analysis of children in Germany also found an inverse association between serum PCBs and body weight (Link et al. 2005
). Typically, higher BMI for adults is associated with higher serum concentrations of these compounds (Bilau et al. 2009
; Collins et al. 2007
; Michalek et al. 1996
). However, in a follow-up analysis of the Seveso cohort, neither BMI nor percent body fat was associated with serum dioxin concentrations after adjustment for sex (Landi et al. 1998
). The metabolism of dioxins and PCBs between children and adults are dissimilar in some respects, with dioxin-like compounds having shorter half-lives among children compared with adults (Kerger et al. 2006
). In children, these lipophilic compounds may be more likely to be sequestered in the body fat or, for those with higher BMI, increased growth may have resulted in dilution of dioxin-like compounds.
We investigated other measures of adiposity, such as waist circumference, waist-to-hip ratio, and clinical assessment of body fat, and found that the inverse associations between BMI and serum dioxin and PCB concentrations were consistent across these measures. Based on these preliminary findings, bioelectric impedance measurements have been added to the study to assess adiposity, so that future analyses may clarify the association between BMI and body composition with serum dioxins and PCBs in this cohort of boys.
Residence near or maternal occupation at the chemical plant, local gardening, and the consumption of local foods were predictors of higher serum dioxin and PCB concentrations among the boys. These data suggest that people who reside near a contaminated area may need to be aware of potential risk for exposure through contact with local soil or consumption of local foods. Although consumption of some local foods contributed to dioxin and PCB exposure, it is important to consider that these locally grown foods are also important components of a nutritious diet for the children of Chapaevsk. Recommendations to reduce children’s exposure include remediation of soil, which is ongoing in specific highly contaminated areas, or relocating gardens and plots to areas with lower contamination.