DDT exposure linked to obesity in later generations

Exposure to the insecticide DDT may cause some people to undergo genetic mutations – which cause later generations of their offspring to be much more susceptible to obesity, suggests a report published in BMC Medicine.

Though DDT (dichloro-diphenyl-trichloroethane) has been banned in the United States since 1972, it was widely used throughout the 1950s.

“I believe most people feel the entire population was exposed, because it was used for 10 years extensively in North America,” Michael Skinner, of Washington State University, told FoxNews.com.

The once-maligned chemical has recently been reintroduced in Africa and other parts of the world in an attempt to reduce malaria deaths, prompting Skinner and his colleagues to initiate an investigation into the long term health effects of the chemical.

“We wanted to investigate DDT, because it’s starting to be used worldwide again,” Skinner said. “We need to start looking at what happens to the individual exposed and how it might be transferred to subsequent generations.”

For his study, Skinner and his colleagues exposed pregnant female rats to DDT for one week, during the critical time in fetal development when the ovaries and testes are forming. The subsequent offspring were then bred to produce a second and third generation of rats. None of the follow-up generations of rats were exposed to DDT.

“That’s called a transgenerational experiment in that we’re seeing what effect the exposure has on the fetus exposed and then a couple generations later,” Skinner said.

Though the effects of DDT were not noticeable in the first or second generations of rats, researchers noticed that 50 percent of the rats in the third generation had developed obesity and a range of other metabolic conditions – including kidney disease, testes abnormalities and polycystic ovarian disease.

“We’ve seen low levels of obesity in the 15 to 20 percent range with (exposure to) other compounds, but over 50 percent was a big surprise to us,” Skinner said.

According to Skinner, exposure to DDT appeared to trigger epigenetic changes in the rats, which occur when environmental factors alter the way DNA is expressed.  The mutation was passed down through the sperm or egg of each rat, which was why the effects of DDT exposure were not visible in the first generation of rats.'

Based on his findings, Skinner believes that human exposure to DDT in the United States throughout the 1950s could be a contributing to the nation’s current obesity epidemic.

“Now if you think about this, when the entire North American population was exposed to DDT in the 1950s extensively for almost 10 years, we’re now three generations from that exposure now,” Skinner said.

Though DDT was banned in the United States decades ago, Skinner points out that the chemical has an extremely long half-life of 25 to 50 years, meaning it is still present as an environmental contaminant.

“It sticks around for 100s of years; it’s not broken down,” Skinner said. “Currently, if you were to go out to almost any rivers in the U.S., and dig down an inch or two into the river, one of the main contaminants you will find is DDT.”

Due to the fact that DDT remains in the environment for such extended periods of time, and has now been linked to transgenerational incidences of obesity and other metabolic diseases, Skinner hopes that other nations will think hard about introducing DDT back into their populations. However, he also acknowledges that if DDT can be used to curb malaria in Africa, it also has the potential to save millions of lives.

“It’s a difficult decision, but if we’re going to make that decision, we have to know all the facts. And one is that you are going to have a transgenerational effect in humans and animals,” Skinner said.