Poster: Long-term mortality in a residential cohort exposed to inorganic hexavalent selenium through drinking water
- Details
- Published on Thursday, 22 October 2015 14:00
Background
Little is known about the health effects of the selenium found in drinking water, and the evidence from human studies on dietary organic selenium is of limited relevance when assessing this issue, due to the distinctive toxicological and nutritional properties of the inorganic species of this metalloid generally found in drinking water.
Methods
In this study, we extended a previous retrospective follow-up of a cohort of 2065 residents in the Reggio Emilia municipality, who had inadvertently been exposed to unusually high levels of hexavalent selenium (selenate, 8 μg/Se/l) through drinking water since 1974 until 1985. We evaluated mortality from major causes in the 1986-2012 period and in the two periods 1986-1997 and 1998-2012, using the remaining municipal residents as referent population and adjusting the comparisons for age and gender in a Cox proportional hazards model.
Results
In the whole follow-up, overall mortality from cancer and from cardiovascular disease in the exposed cohort showed little variation compared with the unexposed population. However, some site-specific cancers such as cancer of the buccal cavity, melanoma, cancer of urinary organs and lymphoid malignancies showed an excess mortality in the selenium-exposed cohort, though these increases were statistically unstable due to the small number of cases. Mortality from nervous disease was also increased, due to an excess mortality from Parkinson's disease and amyotrophic lateral sclerosis. Gender-specific analysis highlighted a few relevant differences. The excess mortality from site specific cancers and neurodegenerative disease consistently decreased over time, suggesting a vanishing effect of selenium exposure over time.
Conclusions: Study results, consistently with findings from recent large randomized trials with organic selenium, suggest that long-term exposure to inorganic selenium in drinking water close to the maximum allowed concentration may have adverse effects on human health. A reassessment of the safe upper limit of selenium in drinking water is warranted.
