2005 Fiscal Year Final Research Report Summary
A Historical cohort study of cancer mortality and offspring sex ratio among municipal solid waste incinerator workers
| Project/Area Number |
14207018
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Hygiene
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| Research Institution | National Institute of Occupational Safety and Health, Japan |
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Principal Investigator |
MORI Ippei National Institute of Occupational Safety and Health, Japan, Department of Hazard Assessment, Senior Researcher (70275345)
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| Co-Investigator(Kenkyū-buntansha) |
OGAWA Yasutaka National Institute of Industrial Health, Department of Work Stress Control, Director (60167319)
KODA Shigeki Kochi Medical School, Department of community Nursing Science, Professor (50205332)
KUMAGAI Shinji Osaka Prefectural Institute of Public Health, Department of Environmental Health, Director (50250329)
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| Project Period (FY) |
2002 – 2005
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| Keywords | municipal solid waste incinerator / dioxins / risk of cancer / reproductive toxicity / sex ratio / cohort study |
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| Research Abstract |
1. Construction of the cohort
With the collaboration of the trade union, we asked municipal solid waste workers to join the cohort study. Finally, 2,866 workers having a work history at municipal solid waste incinerators (exposed group) and 6,239 waste collection workers (reference group) answered to the baseline survey questionnaire. To make rapid evaluation of cancer mortality, we tried to construct a retired workers cohort but it was not possible mainly due to strong social concern on privacy protection.
2. Assessment of exposure to dioxins among incinerator workers
It is not feasible to measure blood dioxin levels for all cohort members. Therefore, we generated several surrogate exposure indices from baseline data such as duration / frequency of exposure to fly ash obtained by self-administrated questionnaire. Those indices were validated by comparing with blood dioxin levels in the subgroup of 58 waste incinerator workers. A correlation was observed between duration of exposure (sum of the period of work exposed to fly ash) and HpDF (one of the PCDD/F congeners) concentration.
3. Evaluation of cancer mortality
Since the cohort consists of active workers only, the population is too yang to evaluate risks of cancer mortality. We need further follow-up for more than 10 years to reach conclusions.
4. Effects on offspring sex ratio
We examined offspring sex ratio as an index of effect on reproductive system. Analysis using surrogate exposure indices showed association between longer period of exposure and lower sex ratio (fewer male offspring), though it was not statistically significant. The association did not change after adjusting maternal parity, paternal age at birth and the year of birth. However, the sex ratio was higher in the shortest exposure group than in the control group. The evidence is not strong enough to discuss relationship between fly ash exposure and offspring sex ratio. Further research is necessary.
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