DOI: 10.14457/tu.the.2019.1580
title: Health risk assessment of exposure to multiple heavy metals among children living in a Vietnamese informal e-waste recycling village

description: Inappropriate handlings of informal e-waste processing have increasingly become a global environmental and public health issue of concern. Humans, particularly children, are vulnerable to the impacts from exposure to heavy metals in different environmental media through several routes, including ingestion, inhalation, and dermal contact from e-waste processing facilities. There is a lack of studies investigated the environmental pollution and human health risks caused by heavy metals exposure from non-intensive e-waste processing activities. Few studies have assessed the aggregative health risks caused by various heavy metals through multiple environmental media and then determining the contribution of different exposure pathways to the estimated risks. None of the studies were conducted to compare carcinogenic and non-carcinogenic risks caused by heavy metal exposures to children from the exposed and reference areas in Vietnam. Limited studies were conducted focusing on the combined effects of mixed metal exposure on children’s health. This study was conducted from January to December 2018 in an informal e-waste processing village (exposed village) and a reference village locating in My Hao District, Hung Yen Province, Northern Vietnam based on the environmental, biological samplings, and questionnaire surveys. The objectives of the study are to (1) quantify the concentration of heavy metals in drinking water, cooked rice, surface dust, and soils; (2) estimate total average daily intake (ADI), carcinogenic and non-carcinogenic risks of heavy metals via ingestion of drinking water, cooked rice and soil, and dermal contact of soil to children; (3) quantify the concentrations of blood heavy metals, evaluating DNA damage, and IQ levels; (4) elucidate the correlation between concentration of heavy metals in different environmental media, carcinogenic and non-carcinogenic risks, blood heavy metals, DNA damage, and IQ levels; and (5) identify the effects of socio-demographic variables to the carcinogenic and non-carcinogenic risks, blood heavy metals, DNA damage, and children’s IQ levels.The results showed that drinking water was safe for heavy metal exposure in both of the villages studied. The mean number of Ni found in cooked rice at the exposed village reached 4.94 times higher than that found at the reference village (p &lt; 0.01). At the exposed village, the levels of heavy metals found in indoor soil were, in descending order, Pb &gt; Ni &gt; Cr &gt; As &gt; Cd. The average concentrations of Pb, Cd, Cr, Ni, and As in indoor soil were 3.55, 9.17, 1.92, 4.53, and 1.08 times, respectively, higher than those in outdoor soil at p &lt; 0.01. The levels of Pb and Cd found in indoor soil samples at the exposed village were 9.49 and 3.26 times, respectively, higher than the maximum allowable limits in Vietnam. The levels of Pb, Cd, Cr, and Ni in indoor soil and surface dust in the exposed village were significantly higher than those in the reference village at p &lt; 0.01. Significant correlations between the pairs of the heavy metals in a medium and between the pairs of the environmental media in which a heavy metal was found at the exposed village suggested that inappropriate activities conducted at an informal e-waste processing facility could be a major contributor to the heavy metal contaminations in the exposed village.The findings revealed that levels of the average daily intake (ADI) of the five heavy metals collected from a child at the exposed village were 3.90 times higher (p &lt; 0.01) than that of a child at the reference village. Ingestion of cooked rice was the largest contributor to the total ADI of the children tested in both villages. However, the risks from water drinking and dermal contact of soil were negligible. The total carcinogenic and non-carcinogenic risks in an exposed child were 1.63 and 4.70 folds higher (p &lt; 0.01) than their respective risks in the reference children. The non-carcinogenic risk to an exposed child was likely to occur, while the risk to a reference child was negligible. The carcinogenic risks found in children from both of the villages, however, were higher than the acceptable values, indicating the potential health risks to the children from both villages. Blood levels of nickel and arsenic in the children at the exposed village were significantly higher than those at the reference village at p &lt; 0.05; however, no significant differences were observed for lead, cadmium, and chromium in children’s blood between the two villages. The overall levels of five heavy metals in exposed children’s blood were significantly higher than those in non-exposed children at p &lt; 0.01. The DNA damage of the children at the exposed village was significantly greater compared to that of the children at the reference village at p &lt; 0.01. Otherwise, there were no significant differences in children’s IQ among the two villages.There were positive correlations between total ADI and carcinogenic risk and DNA damage of children in both villages. The blood arsenic level, overall blood metal levels were positively correlated with DNA damage of children studied. Otherwise, negative correlations were observed between IQ and DNA damage of children in both villages. However, there was no relationship between blood metal levels and children’s IQ. Furthermore, the parental, child engaged in e-waste processing activities, distance to the nearest e-waste processing area, processing e-waste at home, engaging e-waste processing while pregnant, and breastfeeding while processing e-waste was the significant contributing factors to higher health effects on children. These findings pointed out that higher exposure to e-waste would lead to higher carcinogenic and non-carcinogenic risks, higher blood metal levels, higher levels of DNA damage in the exposed children as compared to the reference children. This study highlighted the importance of release mitigation of a hazardous heavy metal from an informal e-waste processing facility to prevent its potential effects on human health.