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Extramural Papers of the Month

By Jerry Phelps
August 2007

Semen Quality Lower when Mother's Beef Consumption High during Pregnancy

Men whose mothers consumed beef more than seven times per week during pregnancy had lower sperm counts as adults, according to new research results from a team of investigators led by an NIEHS-grantee. The researchers conducted an epidemiologic study of 387 men. They found that lower semen quality was associated with more frequent beef consumption by mothers. However, the researchers cautioned that more research is necessary before any substantial conclusions about causation can be reached.

The study points out that all the men were able to father a child without medical assistance. However, the 51 men whose mothers ate the most beef had sperm counts classified as sub-fertile according to standards established by the World Health Organization. In contrast, the men whose mothers ate the least amount of beef had average sperm concentrations 24 percent higher. The men's own consumption of beef was not associated with decreased semen quality nor was the mothers' consumption of other meats.

The authors suspect that in utero exposure to growth hormones and other chemicals present in beef may have altered testicular development. This is but one explanation for these findings; there are several other possibilities, including pesticides in cattle feed and other lifestyle factors during pregnancy.

Citation: Swan SH, Liu F, Overstreet JW, Brazil C, Skakkebaek NE.( Exit NIEHS 2007. Semen quality of fertile US males in relation to their mothers' beef consumption during pregnancy. Hum Reprod 22(6):1497-1502.

Iron and Paraquat - Synergistic Risk Factors for Parkinson's Disease

Mice exposed to iron and the pesticide paraquat showed accelerated age-related damage in neurons associated with Parkinson's disease, according to an NIEHS-funded study. However, mice pretreated with an antioxidant had less severe effects, suggesting iron and paraquat damage the neurons through oxidative stress mechanisms.

Both high doses of iron given at infancy and paraquat have been shown to cause Parkinson-like symptoms in mice. In the current study, genetically identical mice were divided into four groups. One group was given excess iron during infancy; one group was given paraquat; a third group was given both agents; and the fourth group didn't receive either agent. Half the animals in each group were given an antioxidant. Results show that exposing the mice to both agents accelerated the Parkinson-like neurodegeneration with the symptoms starting at the human equivalent of middle-age. Mice co-treated with the antioxidant showed significantly less nerve cell death in the area of the brain associated with Parkinson's disease.

This study points to the need for an early diagnostic test for Parkinson's disease to identify people in need of antioxidant interventions prior to the development of symptoms. It also shows that seemingly harmless early life exposures can work in concert with subsequent exposures to exacerbate neurodegeneration.

Citation: Peng J, Peng L, Stevenson FF, Doctrow SR, Andersen JK.( Exit NIEHS 2007. Iron and paraquat as synergistic environmental risk factors in sporadic Parkinson's disease accelerate age-related neurodegeneration. J Neurosci 27(26):6914-6922.

Cancer Deaths Still High Decades after Exposure to Arsenic Reduced

Death rates from lung and bladder cancer remained high decades after residents of northern Chile were exposed to high levels of arsenic in their drinking water, according to an NIEHS-funded report published in the Journal of the National Cancer Institute.

The northern region of Chile draws much of its water supply from arsenic-contaminated rivers originating in the Andes. From 1958-1970, the municipal water supply for this region averaged 870 micrograms arsenic per liter, nearly 90 times the current U.S. EPA standard. The world's first large-scale arsenic removal plant opened there in 1971, but by then, residents had been exposed to high levels of arsenic for 13 years.

The researchers analyzed cancer death rates in the high-exposure area and compared them to another region in Chile with similar demographic characteristics, but with low arsenic exposure. They found that lung and bladder cancer mortality rates started to increase in 1968 and peaked between 1986 and 1997 with rates reaching 153 per 100,000 men and 50 per 100,000 women - over 2.5 times higher than in the area of lower arsenic exposure.

This study points out the need for more testing of the world's water resources. The results show that the health risks of consuming arsenic-contaminated drinking water are very high and long lasting.

Citation: Marshall G, Ferreccio C, Yuan Y, Bates MN, Steinmaus C, Selvin S, Liaw J, Smith AH.( Exit NIEHS 2007. Fifty-year study of lung and bladder cancer mortality in Chile related to arsenic in drinking water. J Natl Cancer Inst 99(12):920-928.

Men with Higher Bone and Blood Lead Levels at Greater Risk for Heart Disease

A recent NIEHS-sponsored report using data from the Normative Aging Study initiated in 1961 by the Department of Veterans Affairs shows links between exposure to lead and the risk of heart disease in aging men. The study participants consisted of 2,280 middle-aged and elderly men living in Massachusetts. Men with the highest blood or bone lead levels had more heart attacks or angina than men with lower overall lead exposure.

An ischemic heart disease event, defined as myocardial infarction or angina pectoris confirmed by a cardiologist, occurred in 83 cases (70 non-fatal and 13 fatal). The average blood, tibia, and patellar lead concentrations were higher in the ischemic heart disease cases than in controls. The lead levels correlated with about a 25 percent increase in risk for ischemic heart disease.

Lead exposure is known to cause neurological damage in children and also to be a risk factor for hypertension and kidney disease. The current findings further the understanding of the long-term consequences of lead exposure and strongly suggest that the health effects of lead can persist long after the initial exposure occurs.

Citation: Jain NB, Potula V, Schwartz J, Vokonas PS, Sparrow D, Wright RO, Nie H, Hu H.( Exit NIEHS 2007. Lead levels and ischemic heart disease in a prospective study of middle-aged and elderly men: the VA Normative Aging Study. Environ Health Perspect 115(6):871-875.

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