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Exposure to formalehyde – emitted by cars – can decrease semen quality in men, study finds

Inhaling large amounts of formaldehyde released from cars, burning wood and factories can reduce sperm quality, a study has suggested.

Chinese researchers followed 205 young men, more than half of whom worked in a sawmill where burning wood led to high levels of the chemical lingering in the air. They found that this group had less mobile sperm than those in an office position.

The researchers blamed formaldehyde for the decline, pointing to previous research showing it damages tissue and causes inflammation, which affects sperm quality. But 80 percent of participants smoked and six in 10 drank alcohol, both known to affect sperm quality, suggesting other factors may be to blame as well.

Male sperm counts have been declining for decades, raising concerns about fertility. A growing body of evidence suggests that pollution — from chemicals such as formaldehyde — in addition to a more sedentary lifestyle may be behind the decline.

Formaldehyde is common in the air.  It is released when burning wood, industry and when burning fossil fuels - meaning it is also emitted in the exhausts of cars (file photo)

Formaldehyde is common in the air. It is released when burning wood, industry and when burning fossil fuels – meaning it is also emitted in the exhausts of cars (file photo)

Researchers from Xi’an Jiaotong University in Xi’an, central China, conducted the study in June last year.

The participants were on average about 29 years old, lived in the area and worked in the wood industry for a minimum of two years.

They also had a BMI of about 24, which is just in the healthy range of 18.5 to 24.

Men have better quality sperm if their ancestors had large families

Men from larger families generally have better-quality sperm, a study shows.

Researchers at the University of Utah found that men whose ancestors had more children have more healthy-moving sperm.

By comparing the men’s sperm to the number of children in nine generations of their predecessors, it was found that for each additional child in the family history, the subject’s sperm count increased by 1.8 million.

The struggle to conceive can also be inherited as smaller families seemed to go on for generations.

They were divided into two groups, with 124 working in environments with high formaldehyde levels, while the 81 remaining were in those with low levels.

Formaldehyde is a naturally occurring chemical found in the air worldwide, although normally in very low concentrations.

It is emitted when burning wood at home or in forest fires, but also when burning fuel — such as by cars — and through industrial processes.

Tests show that everyone is exposed to at least some formaldehyde every day, although the US Occupational Safety and Health Administration says it should be kept below 0.75ppm.

There is concern that at higher concentrations it could increase the risk of cancer, breathing problems and skin rashes.

To find out how much formaldehyde participants were exposed to, a detector was used to measure the levels in the air.

For those in the formaldehyde group, this was 1.2 parts per million (ppm) — more than 50 percent higher than the safe level in the US, while in the other group these were only trace amounts.

By comparison, in major cities like New York, levels don’t rise above 0.002 ppm even during rush hour.

Within two weeks of the measurements, the participants were asked to masturbate in a cup, after which the semen was studied for up to an hour after.

The sperm of people exposed to formaldehyde was about 0.99 percent less mobile than those of the other group.

It was also more likely that their sperm had not formed correctly and had mutations in the DNA.

There was no reduction in the number of sperm detected in the control group or the formaldehyde group.

Scientists blamed formaldehyde for the reduction in sperm quality, saying studies had shown it could lead to a lack of oxygen to tissues or oxidative stress, causing tissue damage and inflammation.

They added that there is already evidence that some environmental pollutants can also reduce sperm quality.

dr. Mo-qi Lv, the pathologist who led the study, and others said: ‘This study found a link between long-term occupational exposure to formaldehyde and sperm quality.

“This deterioration was dose- and time-dependent and may be caused by oxidative stress.”

The research was published this week in the journal JAMA network opened.