Body Loadings and Health Assessment…(Janet K. Y., Chan Guan & the others)

Review and Comments by Macceau Medozile

In 2007, Janet K.Y. [et al.] published a research paper (in Environmental Science Technology) on body loadings and health risk assessment of polychlorinated dibenzo-p-dioxins (PCDD/Fs) and dibenzofurans at an intensive electronic waste recycling site in China. The primary objective of that case-control study was to carry out a health risk assessment in order to investigate body burdens of dioxins of local residents at Taizhou (TZ) region, since China receives about 70% of the industrial world e-waste and discarded 4 million Personal Computers (PC) annually.

E-waste recycling in China is done by rudimentary methods such as burning wire piles to recover metals, melting circuit boards over coal grills to release valuable chips, cooking computer cases to remove combustible plastics, etc. Ante-studies have indicated that uncontrollable burning and waste disposal are likely to cause serious threats to workers’ health and local residents. The investigators targeted a case group of child-bearing-aged women (24 +/- 2.83 yrs. old) at an e-waste site (Taizhou), from which 40% were primiparae (first time mother) and a reference site (Lin’an city, Zhejiang Province) located at 245 km from TZ, where about the same age group women (24 +/- 2.35 trs. old) was targeted; but this time, the entire population was primiparae. Human milk, placenta and hair samples were collected at each study site from 10 women. The criteria of selection was based upon subject’s residence (living in study site at least for 2 years) and willingness to donating sufficient hair and milk specimen for chemical analysis; an informed consent was completed prior to the specimen collection. Additionally, socio-demographic data and food consumption habits of the study population were obtained through direct interviews and questionnaires.

About 100 mL of human milk (breast milk) was collected 4 ½ days after birth, the placenta was collected the day of delivery and about 3 grams of hair _ sampled from near the scalp and the nape of the neck _ was also collected the first day after delivery. All the specimens were frozen immediately after collection and stored at -20o C until chemical analyses were conducted. Levels of PCDD/Fs were indicated as mass concentration and toxic equivalency (TEQ) of the World Health Organization’s model of 1998. The body burdens were expressed as pictogram (10-12 g.) of dioxin, TEQ per gram of fat in human milk and placenta.

The quantitative data analysis was done by using “The Statistical Package for Social Sciences” (SPSS of Windows, version 11.0) and Pearson correlation coefficients (p) were used to determine relationships between different parameters.

The study indicated that demographic characteristics and food intake were the primary factors affecting dioxin levels. The total TEQs increase with the length of residence in TZ and the number of spontaneous abortions of the donor (a similar study was also conducted in Russia in contrast to Takekuma et al. where there was no significant correlation between residence years and TEQ values of human milk). Although other studies indicated a strong correlation between dioxin levels in human specimens and mother’s age, Janet’ study showed that dioxin levels did not vary significantly by mother’s age. The author referred to limited sample size and narrow age range as factors that might prevent the data collected from showing such correlation. However, the study showed that there was a statistically significant increase in TZ milk dioxin levels with the intake of crab and egg. Moreover, the TEQ values of TZ placenta was also significantly correlated with the intake of crab, whereas TZ milk fat proportion indicated a significant correlation with the intake of shellfish.

On the other hand, there were statistical correlations between the reference site (HZ) body loading and the intakes of food of animal origin. The total toxic equivalency of HZ human milk was two times lower than TZ’s (9.35 pg WHO TEQ/g versus 21.02 pg WHO TEQ/g). TZ placenta and TZ hair showed greater concentration than HZ’ samples. The study indicated that background pollution level, dietary habits and personal characteristics of the donors were the most important factors affecting the body burden in HZ. It’s likely that human exposure to dioxin begins with atmospheric emissions, of which incineration releases the largest quantity of dioxins. Therefore, the author concurred that background contamination in TZ should be greater than that in HZ. The study showed that levels of dioxin in TZ hair samples were significantly higher than that in HZ’s.

In this study, hair sample was found to be the most effective bio-marker (of exposure). The placenta was ideal for bio-monitoring as it is large enough to allow assay for several pollutants during the same sampling and human milk, convenient and non-invasive, was very replicable. When comparing the three types of specimens from TZ, the investigators found a concentration level of dioxin two times higher than WHO-TEQ/g dry wt benchmark level (33.82 +/- 17.74 pg ; p = 0.001), followed by human milk (2.96 +/- 1.30 pg WHO-TEQ/g dry wt) and then placenta (2.06 +/- 1.30 pg WHO-TEQ/g dry wt). Samples from HZ also showed a similar trend whereby PCDD/F concentration in hair (5.59 +/- 4.43 pg WHO-TEQ/g dry wt) were significantly higher than those in placenta (0.63 +/- 0.28 pg WHO-TEQ/g dry wt) and milk (2.20 +/- 1.45 pg WHO-TEQ/g dry wt; p> 0.05).

So, even though the sampling population was very small (2.5: 100,000 people in TZ and 1.9: 100,000 in HZ; gender ratio for both regions was not provided), the study suggests that heavy body burden of dioxin in mothers is correlated with e-waste exposure (and similar investigation in Japan indicated that women who were exposed to co-contaminants, mostly PCB-contaminated rice oil from Taiwan showed significantly higher level of dioxin contamination in their placenta). Infants in TZ consumed over two times TEQ/kg body wt/day than those in HZ (102.98 +/- 67.65 pg TEW/kg body wt/day, 45.83 +/- 36.22 TEW/kg body wt/day); both values exceed the WHO Tolerable Daily Intake (TDI).

Reference:

1. Janet K.Y, Chan, Guan [et al.], Body loadings and health risk assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans at an intensive electronic waste recycling site in China. Environmental Science Technology, vol. 41, No. 22. 2007
2. Silicon Valley Toxics Coalition. Just say no to e-waste: Backround document on hazards and waste from computers. http://www.svtc.org/cleancc/pubs/sayno.htm
3. WHO. Fact sheet: dioxin and their effects on human health. http://www.who.int/mediacenter/factsheets/fs225/en/
4. Taizhou Municipality, China. http://www.zjtz.gov.cn/ksp/english
5. Neuber, K; Merkel, G [et al.]. Indoor Air Pollution by lindane and DDT indicated by head hair samples of children. Toxicol. Lett. 1999, 107, 189-192.

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