Ozone does damage. So does nitrogen dioxide. At least that is what a massive new fertility study suggests about how pollutants interact with human genetics. It’s not about the code itself changing, though. The letters of the DNA sequence stay the same. But the switches? The lights go off where they shouldn’t. Or flip on at the wrong time.
The research dropped Tuesday in London during the European Society of Human Repression and Embryology’s annual meeting. It’s one of the largest studies of its kind. It tracked over 2,00 men in Salt Lake, Utah between 2013 to 2017. They provided semen samples. Once. Then again two months later. Four. Six. It’s a long time for sperm, considering how quickly it cycles, but this covered multiple generations of cells.
“Our findings suggest that air pollution exposure… may be associated with changes in sperm dna.”
Dr Carrie Nobles
That quote is from the lead epidemiologist. Dr Carrie Nobles from the University of Massachusetts Amher she calls them epigenetic changes. Fancy words for a messy reality. Basically chemical tags called DNA methylation get slapped onto your genes. They decide whether a gene wakes up or stays asleep. The study found 39 distinct changes in the men who were exposed to high levels of pollution just three months before they handed in their samples. Three months. That’s exactly how long it takes to make sperm.
So if you are standing in the smog while those cells form they get marked up. Ozone was the biggest offender. Nitrogen dioxide followed closely behind. Sulfur dioxide and particulate matter were part of the mix but those two led the charge.
Does it matter? Well. Most of these epigenetic tags get scrubbed clean when a baby starts to develop in the womb. It’s a reset button. But some genes stick. They are “imprinted”. One specific gene called GNAS showed up in this research. We already know GNAS matters. It affects semen quality. It impacts fetal development. If air pollution messes with that gene it’s not just about getting pregnant. It might affect the health of the resulting child too.
Prof Allan Pacey at the University of Manchester was careful though. He wasn’t part of the team but he watched the data. He said we have a measurable effect here. But meaningful is a different word. Clinically significant? We don’t know yet. The link is there. The causality for infertility rates remains murky.
Still. The trend is scary.
Prof Richard Lea at Nottingham sees the writing on the wall. He thinks this adds weight to the growing consensus. Sperm quality is suffering. And we are breathing it in every day.
So you mask up? Maybe. But will a filter stop ozone from tagging your DNA? That seems like a hard question. We have plenty of data now. But not enough certainty to sleep easy at night. Or to stop the traffic outside your window.
We’ll just have to wait for the next study.
