Friday, 25 July 2014

Pesticide Exposure and Obesity, Kidney Disease and Ovarian Disease

Researchers at Washington State University have discovered that when a pregnant mouse is exposed to a pesticide called methoxychlor, three generations of her descendants experience an increased risk of obesity, kidney disease and ovarian disease. The risk of more than one of these diseases occurring at the same time is highest in her great-grandchildren. This discovery is worrying because observations in mice often apply to humans, too.

Methoxychlor was once used to treat crops in the United States.
Public domain photo
by R0bin
Methoxychlor was once a common pesticide and is still used in some parts of the world. It was used as a replacement for DDT on crops, ornamental plants, livestock and pets. Methoxychlor was banned in 2003 in the United States because it was found to disrupt the human endocrine (hormonal) system.

Since methoxychlor was banned eleven years ago, people might think that it's no longer a danger. According to the mouse research, however, this assumption is wrong. The researchers believe that methoxychlor affects how genes are turned on and off and that this effect is somehow passed from one generation to the next.

Genetics is the study of genes and inheritance. Genes give us many of our characteristics. However, not all of our genes are active at any one time. Epigenetics is the study of how genes are turned on and off. The ability of a chemical exposure in a female of one generation to affect epigenetics in a subsequent generation is known as transgenerational epigenetic inheritance.

The researchers discovered that a female mouse's exposure to methoxychlor "at a range typical of high environmental exposures" increased the risk of specific health problems in her children, grandchildren and great-grandchildren. In addition, they found that the epigenomes in the sperm of the male great-grandchildren of the affected female were also altered. An epigenome is a collection of chemicals that affect genes.

The University of Washington scientists suggest that the increasing incidence of obesity today could be due to our ancestors' exposure to methoxychlor. Whether or not this is the case, the mouse discovery does suggest that we need to be careful about our chemical exposure not only for the sake of our own health but also for the sake of our descendants' health.