Residual DDT and PCBs in the environment cause birth defects and male infertility.

Organochlorine chemicals, such as DDT and PCBs, were banned in the United States in the 1970s, but that doesn’t mean they’re gone.

In fact, a new study suggests that organochlorines are still causing infertility and birth defects.

“Years after DDT has been phased out in most countries, we are still learning about the effects of a so-called ‘legacy pesticide’ that persists in the environment for years after its use,” said Emily Marquez, Ph.D., a senior scientist at the Pesticide Action Network.

As exposure to DDT and PCBs goes up, so does the rate of sperm with extra chromosomes.

The researchers measured men’s serum levels of DDE (the metabolized form of DDT) and PCBs. The higher their exposure, the more abnormal sperm they had.

This mutation, the researchers observed, most often resulted in infertility or early miscarriages. As many as half of early miscarriages happen because the fetus has an abnormal set of chromosomes. Sometimes the extra chromosomes can result in children with birth defects.

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Previous studies had linked the chemicals to sperm, showing that they diminish sperm count and motility. But chromosomal abnormalities are a bigger problem, and this study appears to be the first to link them to chemical exposure.

Melissa Perry, Ph.D., chair of the environmental and occupational health department at the Milken Institute School of Public Health at George Washington University, and her team focused on Danish men in the Faroe Islands.

The population is known to have higher exposures to organochlorines. The chemicals concentrate in larger marine predators and Faroe Islands residents eat pilot whale.

“If you see an abnormality in the number of chromosomes, you know exactly that that’s going to cause a problem. The offspring is going to have that extra chromosome,” Perry told Healthline.

The new findings also point to the long-term effects that exposure has on male fertility. Some of the study participants had been tested for chemical exposure at age 14. Their levels were then synced with their rates of sperm abnormalities at the time of the study.

“A lifetime of exposure is increasing one’s risk,” Perry explained.

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It may seem that organochlorines are a problem of the past in the United States, but the chemicals have lingered in the food and water supply.

Long-term, low-grade exposure has resulted. At low levels, the chemicals interfere with the body’s responses to the hormone estrogen.

In an earlier U.S. study focusing on men who had sought care with their partners at a Boston fertility clinic, Perry saw the same correlation between chemicals in the blood and extra chromosomes in the sperm.

Many developing countries continue to use DDT indoors to kill the mosquitos that spread malaria. In the United States, the debate over DDT hasn’t entirely ended. Some have argued that DDT should also be used domestically to prevent malaria.

When it comes to chemicals like DDT and PCBs that resist breaking down over time, what happens in one country doesn’t stay in that country. The chemicals met with international condemnation when they were found in the Arctic, far away from anywhere they’d ever been used.

The disagreements over the risks of DDT and PCBs have more or less been settled. But other chemicals, many of which interfere with human hormonal functions, are now at the center of a similar debate.

Many chemicals that remain in wide use disrupt the human endocrine system. In a recent study, consumption of U.S.-grown fruits and vegetables likely to retain pesticide residue was correlated with low sperm count and motility.

Other chemicals now in use also accumulate in fat. That property is what has led DDT and PCBs to last longer in the environment. They concentrate in animals near the top of the food chain — such as whale and tuna, but also humans. They’re passed on to infants in breast milk.

These chemicals are the ones that especially worry Perry. It’s not clear that we have mastered the historical lessons of DDT when perfluorinated chemicals (PFCs) are commonly used to make nonstick cookware and stain-resistant fabric, despite the fact that they persist in the environment and have been linked to infertility in both men and women.

“We continue to utilize and depend on chemicals that are persistent without knowing what longer term impacts they may have down the road,” she said. “We’ve done away with (older) persistent compounds. Let’s make sure we’re vigilant about the next class.”

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