An estimation of the health impact of groundwater pollution caused by dumping of chlorinated solvents
Introduction
Uncontrolled hazardous waste sites are major environmental and public health concerns in many countries (Johnson, 1995). In 1994, the Taiwan Environmental Protection Administration (EPA) declared an electronics factory in Taoyuan County, which was operational from 1970 until 1992, a hazardous waste site. From 1999 to 2000, we conducted a site-specific risk assessment on residents in the groundwater-contaminated community downstream from the factory. We performed measurements on groundwater concentrations of seven chlorinated hydrocarbons in the 44 downstream residential wells. Vinyl chloride, tetrachloroethylene and trichloroethylene, were the carcinogenic chemicals classified by the International Agency of Research on Cancer (IARC) as groups 1 and 2A, all affecting the liver as their major target organ based on animal studies retrieved from toxicological databases (U.S. EPA, 2009, ATSDR, 2009). By following the guidance of the U.S. Environmental Protection Agency (U.S. Environmental Protection Agency (EPA), 1989, U.S. Environmental Protection Agency (EPA), 2001a), we found an increased carcinogenic risk based on the scenario of reasonable maximum exposure (RME) (Lee et al., 2002). The increased risk of liver cancer was corroborated by a case-control study, in which male residents in the downstream (exposed) village had an increased mortality odds ratio for liver cancer of 2.57 (95% Confidence interval: 1.21–5.46) compared with those in the upstream (unexposed) area after adjustment for age and period (Lee et al., 2003). The above estimates provided some information on how much could the preventive measures have contributed, had they been proactively taken earlier. However, the above estimates cannot be directly compared with the contribution of other healthcare services and cannot be used to promote prevention on a higher priority in health policy decision.
Quality of life (QOL) is an increasingly important measure of subjective health outcomes of cancer, in addition to an objective indicator of survival (Testa and Simonson, 1996). To perform a comparative health risk assessment, we need to develop an approach using a common unit, such as quality-adjusted life year (QALY), for determining how to effectively spend clinical resources to maximize QALYs (Cohen et al., 2008). Although, as an English proverb says, “an ounce of prevention is worth a pound of cure”, there have been relatively few studies quantifying the expected loss of QALYs due to environmental and/or occupational pollution. The objective of this study is to estimate the total QALYs lost due to the occurrence of liver cancer, and the total expected loss of QALY resulting from groundwater pollution in a north Taiwanese community based on reasonable maximum exposure.
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Methods
Our approach to estimate the health impact from groundwater contamination included two steps: the first step was to calculate cancer risk estimates based on on-site environmental exposure assessment, epidemiological data, and cancer slope factors based on toxicological studies, of which the target organ is the liver; the second step was to evaluate the consequence of the event of pollution by the metric of QALY. In the first step, we derived the estimates of likelihood of cancer from our
Results
A total of 94,144 patients with liver cancer were identified in the Taiwan Cancer Registry from 1990 to 2005. This retrospective cohort consisted of 71,051 men and 23,093 women, with a mean age of 60.6 ± 13.5. Females were significantly older than males (+ 5.1 years). The median survival was 8.5 months for all cases, 7.8 months for male cases, and 11.2 months for females. Table 1 summarizes the epidemiological features of our patient cohort. The average EYLL due to liver cancer was 16.7 years. After
Discussion
This study demonstrated an empirical example of how QALY can be used to comparatively assess the health risk of groundwater pollution with regard to developing cancer. While the usual approach of risk characterization focuses on the quantification of the likelihood of significant health events, this study goes one step further to estimate the expected number of QALY loss. Adopting the concept of risk defined by the British Standard 18004:2008, we quantified the consequence of health outcomes
Acknowledgements
We are very grateful to the Bureau of Health Promotion, Department of Health of Taiwan, for providing the dataset of the Taiwan Cancer Registry cross-linked with death certificate data.
Grant information:The National Health Research Institutes (NHRI) of Taiwan funded this research (NHRI-97A1-PDCO-01-0811-2).
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