Eva Y. Wong

Use of Quality-Adjusted Life Year Weights with Dose-Response Models for Public Health Decisions: A Case Study of the Risks and Benefits of Fish Consumption

Risks associated with toxicants in food are often controlled by exposure reduction. When exposure recommendations are developed for foods with both harmful and beneficial qualities, however, they must balance the associated risks and benefits to maximize public health. Although quantitative methods are commonly used to evaluate health risks, such methods have not been generally applied to evaluating the health benefits associated with environmental exposures. A quantitative method for risk-benefit analysis is presented that allows for consideration of diverse health endpoints that differ in their impact (i.e., duration and severity) using dose-response modeling weighted by quality-adjusted life years saved. To demonstrate the usefulness of this method, the risks and benefits of fish consumption are evaluated using a single health risk and health benefit endpoint. Benefits are defined as the decrease in myocardial infarction mortality resulting from fish consumption, and risks are defined as the increase in neurodevelopmental delay (i.e., talking) resulting from prenatal methylmercury exposure. Fish consumption rates are based on information from Washington State. Using the proposed framework, the net health impact of eating fish is estimated in either a whole population or a population consisting of women of childbearing age and their children. It is demonstrated that across a range of fish methylmercury concentrations (0-1 ppm) and intake levels (0-25 g/day), individuals would have to weight the neurodevelopmental effects 6 times more (in the whole population) or 250 times less (among women of child-bearing age and their children) than the myocardial infarction benefits in order to be ambivalent about whether or not to consume fish. These methods can be generalized to evaluate the merits of other public health and risk management programs that involve trade-offs between risks and benefits.

Adult proxy responses to a survey of children's dermal soil contact activities

Contaminated site cleanup decisions may require estimation of dermal exposures to soil. Telephone surveys represent one means of obtaining relevant activity pattern data. The initial Soil Contact Survey (SCS-I), which primarily gathered information on the activities of adults, was conducted in 1996. Data describing adult behaviors have been previously reported. Results from a second Soil Contact Survey (SCS-II), performed in 1998–1999 and focused on childrens activity patterns, are reported here. Telephone surveys were used to query a randomly selected sample of U.S. households. A randomly chosen child, under the age of 18 years, was targeted in each responding household having children. Play activities as well as bathing patterns were investigated to quantify total exposure time, defined as activity time plus delay until washing. Of 680 total survey respondents, 500 (73.5%) reported that their child played outdoors on bare dirt or mixed grass and dirt surfaces. Among these “players,” the median reported play frequency was 7 days/week in warm weather and 3 days/week in cold weather. Median play duration was 3 h/day in warm weather and 1 h/day in cold weather. Hand washes were reported to occur a median of 4 times per day in both warm and cold weather months. Bath or shower median frequency was seven times per week in both warm and cold weather. Finally, based on clothing choice data gathered in SCS-I, a median of about 37% of total skin surface is estimated to be exposed during young childrens warm weather outdoor play.

Occupational exposures and ovarian cancer in textile workers.

Background: Occupational risk factors for ovarian cancer have been investigated only to a limited extent. We conducted a case-cohort study to examine associations between occupational exposures and ovarian cancer in the textile industry. Methods: We compared 261 incident ovarian cancer cases diagnosed between 1989 and 1998 with an age-stratified reference subcohort (n = 3199) from a cohort of 267,400 textile workers in Shanghai, China. Occupational exposures were assessed by job-exposure matrices designed for the textile industry, and estimates of quantitative cotton dust and endotoxin. We calculated hazard ratios (HRs) and 95% confidence intervals (CIs) with Cox proportional hazards modeling adapted for the case-cohort design. Results: A decreased risk of ovarian cancer was associated with ever having worked in cotton manufacturing production (HR = 0.7; 95% CI = 0.4–1.0). An increased risk was associated with ever having worked in textile finishing (2.1; 0.9–5.0). We found an increasing risk of ovarian cancer associated with cumulative exposure to silica dust (for <10 years exposure, HR = 6.8 [CI = 0.6–76]; for ≥10 years, 5.6 [1.3–23.6]), although these results are based on only 8 exposed subcohort women (0.3%) and 4 cases (1.3%). We also detected inverse risk gradients for cumulative exposures to endotoxin when exposures were lagged by 20 years (in highest quartile, HR = 0.6 [CI = 0.4–1.1]). Conclusion: Silica dust may increase the risk of ovarian cancer, and cotton dust and endotoxin may reduce risk.

Physical activity, physical exertion, and miscarriage risk in women textile workers in Shanghai, China

BACKGROUND Strenuous occupational physical activity and physical demands may be risk factors for adverse reproductive outcomes. METHODS A retrospective study in the Shanghai, China textile industry study collected womens self-reported reproductive history. Occupational physical activity assessment linked complete work history data to an industry-specific job-exposure matrix. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by multivariate logistic regression for the first pregnancy outcome and utilized generalized estimating equations to consider all pregnancies per woman. RESULTS Compared with women employed in sedentary jobs, a reduced risk of miscarriage was found for women working in jobs with either light (OR 0.18, 95% CI: 0.07, 0.50) or medium (OR 0.24, 95% CI: 0.08, 0.66) physical activity during the first pregnancy and over all pregnancies (light OR 0.32, 95% CI: 0.17, 0.61; medium OR 0.43, 95% CI: 0.23, 0.80). Frequent crouching was associated with elevated risk (OR 1.82, 95% CI: 1.14, 2.93; all pregnancies per woman). CONCLUSIONS Light/medium occupational physical activity may have reduced miscarriage risk, while specific occupational characteristics such as crouching may have increased risk in this cohort.

Quality adjusted life years (QALYs) and dose–response models in environmental health policy analysis — methodological considerations

Analyses of competing risks are currently limited by the lack of empirically well-founded and generalizable quantitative methods. Specifically, quantitative methods for comparative risk analysis require the consideration of the population impacted, the duration of impact, the health endpoints at risk, and the impact on individual quality of life. Whereas risk analysis can be used to provide quantitative estimates of disease incidence, environmental health policy analyses do not often account for differences in health impact from alternative disease states. We discuss the methodological issues related to the use of quality adjusted life years (QALY) as a metric for normalizing expected disease incidence to account for health impact. Through a case study of the risks and benefits of fish consumption, we demonstrate the use of QALY weights with dose-response models for environmental health policy decision making. We suggest that, although this approach can be generalized for use in comparative risk and health policy analysis, it is informationally intensive and requires additional assumptions to those used in traditional safety/risk assessment.