A cocktail of chemical pollutants measured in people’s bodies has been linked to declining sperm quality by new research.
Chemicals such as bisphenols and dioxins are thought to interfere with hormones and harm sperm quality, and the study found that combinations of these compounds are present at “amazing” levels, up to 100 times higher than those considered safe.
Bisphenol A (BPA) was responsible for the greatest risks, the scientists said. The chemical is found in milk and canned foods when it leaks from the packaging liner. The most important steps for healthy male sexual development take place during pregnancy, making the study findings particularly relevant for expectant mothers, the researchers said.
Sperm count and concentration had suffered an alarming decline for decades in Western countries, the scientists said sperm count halved in the past 40 years† Other male sexual disorders such as penile deformity, breast cancer and undescended testicles have increased. Hormone-disrupting chemicals are a prime suspect, and the study sheds new light on the potential for chemical cocktails to cause harm.
The research team, led by Prof. Andreas Kortenkamp of Brunel University in London, said they were “astonished at the magnitude of the hazard index,” the risk measure of the chemical cocktails. The team was also surprised that BPA was the most troubling chemical, as previous work had focused on phthalates, which are used in plastics.
Kortenkamp told the Guardian the study would allow for better epidemiological studies in humans to assess the effects. “But personally I think, with the evidence we’ve produced, there’s no reason to delay any regulatory action.”
The research, published in Environment International magazinereviewed measurements of nine chemicals, including bisphenol, phthalates and acetaminophen, in urine samples from nearly 100 Danish men ages 18 to 30. It also used existing data, mainly from the European Food Standards Agency, to estimate human exposure to 20 other chemicals.
These data have been compared to acceptable levels of exposure, also drawn from the scientific literature. This provided a measure of the potential impact of each chemical, which was then summed using an established method to produce an overall measure of risk for the cocktail of chemicals in each of the men.
All men were exposed to unsafe combined exposures, and the most exposed men in the study had levels 100 times higher than tolerable levels, averaging 17 times. “Our assessment reveals alarming exceedances of acceptable combined exposures,” the researchers concluded.
The researchers were also able to rank the chemicals, with BPA being the biggest risk factor, followed by dioxins, acetaminophen and phthalates. However, removing BPA did not reduce the combined exposure to acceptable levels.
Paracetamol has been shown to cause a decrease in sperm quality in laboratory animals and to increase the risk of non-descending testicles in boys born to mothers who use the analgesic during pregnancy. In 2021, a review backed by 90 scientists said: “We recommend that pregnant women are warned at the beginning of pregnancy to refrain from [paracetamol] unless its use is medically indicated, and if unsure, consult a doctor or pharmacist.”
The researchers accepted that there were uncertainties in their analyses. For example, the data used was for the years 2009-2010 and while exposure to BPA has decreased slightly since then, exposure to other bisphenols has increased. It is also possible that young women are not exposed to the same chemical exposure as the young men in the study.
But the researchers said, “Given the multitude of chemicals people are exposed to, these limitations almost certainly mean we underestimated the risks of mixtures.” So-called “forever chemicals,” PFAS compounds, can damage sperm, but were excluded from the study because data is limited. Sky pollution can also affect sperm quality.
In addition to the impact of chemicals, other causes for declining sperm quality have been proposed by scientists, and research suggests: links to body weight, A lack of fysical activity and to smoke†
“We are not saying that chemicals are the only factor,” says Kortenkamp. “Nutritional epidemiologists say eating a lot of fatty foods — cheese, butter, cheap fats, high-fat meats — isn’t good for sperm quality.”
Prof Hagai Levine, at the Hebrew University School of Public HealthIsrael, said: “This is a unique study and adds to the growing evidence about the adverse impact of certain chemicals on human reproduction. We need to step up global efforts to study the causes of male reproductive disruption. .”
Prof Richard Sharpe, at the University of Edinburgh, said: “Unlike the authors of the new study, and many in the scientific community, I remain unconvinced that exposure to weakly endocrine-active chemicals in the environment is a major causal role in fall sperm counts.” He said there was no direct evidence that most of the chemicals reviewed by the study harmed testicular development in humans, although there is good evidence for acetaminophen.
Sharpe said he was convinced that the declining sperm count must have an environmental cause, most likely affecting early pregnancy. But he said a high-fat, processed diet is both harmful in itself and the main source of the chemicals, making it difficult to discern what could be causing it. Nevertheless, Sharpe said it remains possible that some chemical cocktails could negatively affect sperm count in men.
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