Prenatal Low-Level Exposure to Arsenic Linked With Early Onset of Puberty and Obesity

According to a new study conducted by the National Institutes of Health (NIH), mice who were exposed to low levels of arsenic in utero, had an earlier age of onset for puberty and were more likely to become obese once they reached maturity. The findings were published in the journal Environmental Health Perspectives, and they may serve as an accurate predictor of health outcomes in humans as a result of prenatal arsenic exposure.

The arsenic was administered to the embryonic mice through the drinking water provided to their mothers. The researchers found that the arsenic exposure level could be as low as 10 parts per billion (ppb) – the maximum allowable concentration of arsenic in drinking water, as mandated by the US Environmental Protection Agency (EPA) – and still contribute to obesity and early puberty.

Researchers at the National Institute of Environmental Health Sciences (NIEHS), a division of the NIH, tested the effects of arsenic on embryonic development in pregnant mice. The experimental group of mice received the EPA standard of 10 ppb, while a positive control group received a dose equivalent to 42.5 ppb – a level of arsenic that has been previously shown to negatively impact development in mice. A third group of gestating mice acted as a control, and were given water free from arsenic.

The arsenic was administered to the mice between 10 days post-fertilization and birth, which correspond to the mid-point of the first trimester and birth in humans, respectively. “We unexpectedly found that exposure to arsenic before birth had a profound effect on onset of puberty and incidence of obesity later in life,” said Dr. Humphrey Yao, an NIEHS reproductive biologist and co-author of the study. “Although these mice were exposed to arsenic only during fetal life, the impacts lingered through adulthood.”

The effects of the in utero arsenic exposure included obesity and early onset of puberty in female mice, and although the researchers did not record the age at which males reached sexual maturity, they did observe that male mice also gained weight. Both the 10 ppb and 42.5 ppb doses of arsenic caused weight gain in aging mice.

The experiment was performed in three distinct populations of mice – all of which included a positive control, a negative control and an experimental group. The researchers observed similar results in each, according to NIEHS biologist, and primary author Dr. Karina Rodriguez. She warns that although it’s unknown how arsenic affects development, the results reinforce the importance of continued research on the seemingly innocuous substances ingested by expectant mothers, and how they influence long-term health of the offspring.

Dr. Linda Birnbaum, director of NIEHS and the National Toxicology Program says, “It’s very important to study both high doses and low doses. Although the health effects from low doses were not as great as with the extremely high doses, the low-dose effects may have been missed if only high doses were studied.”

Sources:

• Low-level arsenic exposure before birth associated with early puberty and obesity – http://medicalxpress.com/news/2015-08-low-level-arsenic-exposure-birth-early.html
• Rodriguez, K., Ungewitter, E., Crespo-Mejias, Y., Liu, C., Nicol, B., Kissling, G., and Yao, H. (2015). Effects of in Utero Exposure to Arsenic during the Second Half of Gestation on Reproductive End Points and Metabolic Parameters in Female CD-1 Mice. Environ. Health Perspect.