Ecology Center

A recent University of Michigan study has found that some candles on the market today are made with wicks that have either lead or leaded cores that emit potentially dangerous levels of lead into the air. The study, conducted by Jerome Nriagu, a professor of environmental health sciences at the School of Public Health, showed that lead emission rates for candles ranged between 0.5 and 327 micrograms per hour. After one hour, five of the candles tested emitted unsafe levels of lead into the air that measured greater than the Environmental Protection Agency's recommendation of 1.5 micrograms per cubic meter for ambient air. After five hours, the lead levels in an enclosed space ranged from an estimated 0.21 to 65.3 micrograms per cubic meter.

The study tested emissions from 15 different brands of candles made in the United Sates, Mexico and China. Candles produced in China and the United States released the highest levels of lead into the air. According to Nriagu, the levels of lead were small, but still may represent a health risk over a long period of time. "This study shows that there are still other important domestic sources of lead exposure that have escaped public scrutiny and legislative control," said Nriagu. "Leaded candles were recently banned in Australia, and we recommend a similar action in this country."

SOURCE: Not yet published. For more information, contact: Amy Reyes <amelynr@umich.edu>

Bisphenol A Exposures Advances Puberty

Nature Magazine recently reported study findings that show exposure to bisphenol A advances puberty. Researchers found that female mice exposed in the womb to low doses of bisphenol A (2.4 micro-g per kg per day to the mother) had a significantly reduced delay between vaginal opening and first vaginal oestrus. They also used information on litter position in the womb, which showed that those females positioned between female litter mates were most affected by bisphenol A, and those between males were least affected. Bisphenol A is used in the making of many plastics, including polycarbonate and the enamel resin that line many food cans.

SOURCE: Howdeshell, K.L., Hotchkiss, A.K., Thayer, K.A., Vandenbergh, J.G. and vom Saal, F.S. Nature, October 21, 1999, vol. 401 p762-764.

Simultaneous PCB and Methylmercury Exposure Results in Synergistic Effects A new study in Environmental Health Perspectives found synergistic effects in laboratory animals exposed to both PCB's and methylmercury. The researchers measured dopamine levels in the brains of adult rats exposed to polychlorinated biphenyls (PCBs) and methylmercury. Exposure to PCBs only effected dopamine levels in a dose-dependent fashion, and exposure to methylmercury alone did not significantly affect either measure. However, simultaneous exposure to PCBs and methylmercury resulted in significantly greater changes in dopamine levels.

PCBs and methylmercury are common contaminants in fish. Consumption of contaminated Great Lakes fish by pregnant women is associated with decreased birth weight and deficits in cognitive function in their infants and children. The authors conclude: "The synergism between these contaminants suggests that future revisions of fish- consumption guidelines should consider contaminant interactions."

SOURCE: Jeffrey C. Bemis and Richard F. Seegal. Polychlorinated Biphenyls and Methylmercury Act Synergistically to Reduce Rat Brain Dopamine Content in Vitro. Environmental Health Perspectives, November 1999, vol. 107, number 11, pages 879-885.

Pesticide Exposure and Decreased Fertilization Rates

Dr. E. Tielmans and colleagues from the Netherlands investigated the effects of paternal exposure to pesticides on the ability of men's sperm to fertilize women's eggs. Researchers examined 836 couples who sought in-vitro fertilization (IVF) treatment between 1991 and 1998. A detailed survey was made of occupational exposure to hazardous substances. Those men who reported occupational exposure to pesticides were asked additional questions about the nature of their exposure. These data were then compared with data on rates of successful fertilization.

The researchers showed that rates of successful fertilization in IVF treatment were significantly decreased for couples with male partners who were occupationally exposed to pesticides. Those men with the highest exposure to pesticides had only 22% of the fertilization success of a reference group. The researchers comment that "our results are the first to suggest that paternal pesticide exposure decreases the sperm fertilizing ability in vitro", but they caution that since most men in their study were exposed to many types of pesticides, it is difficult to ascertain which chemical affects fertilization ability.

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