It distorts sperm, makes it harder to get pregnant, and can lead to premature births and low birth weights -- yet another reason why cars and humans don't mix well.
Air pollution has become the world's single largest environmental health risk, and scientists say it causes more than 3.7 million premature deaths per year (data from 2012). But what does air pollution do to unborn children? Or even to those parents who are trying to get pregnant? New research shows it's having a seriously detrimental effect.
Problems start with a man's sperm. In a study titled, "Exposure to ambient fine particulate matter and semen quality in Taiwan," researchers from the Chinese University of Hong Kong examined 6,475 men between the ages of 14 and 49 and found that the more air pollution a man is exposed to, the greater his risk of having irregularly shaped and smaller sperm. Most of the participants did not smoke and had less than one alcoholic drink per week.
From Newsweek's report on the study:
"Air pollution was also associated with a 26-percent increase in the risk of being in the bottom 10 percent of average sperm size and shape."
Why? Because air pollution contains particulate matter (PM) that consists of heavy metals (such as cadmium, known to be carcinogenic) and polycyclic aromatic hydrocarbons (PAHs) that have had toxic effects on semen quality in animal experiments. The study says, "Chronic, low-dose exposure [to PM] may contribute to significant spermatogenesis impairment."
This makes it hard for a couple to get pregnant. With 48.5 million couples affected by infertility worldwide, the researchers "advocate global strategies on mitigation of air pollution to improve reproductive health."
But once pregnant, the concerns don't stop there. Another study, titled "Impact of London's road traffic air and noise pollution on birth weight" and just published in the BMJ, examines the impact of London's traffic fumes on growing fetuses.
It found that exposure to air pollution is indeed having a detrimental effect on babies' health, contributing to lower birth weights (at a 2- to 6-percent increase of risk) and premature birth (1- to 3-percent increase of risk). Low birth weight is a concern because it can result in slow growth, developmental delays, susceptibility to infectious disease, and death in infancy and early childhood.
The researchers believe in the need for environmental policies that will reduce road traffic, leading to less air pollution in urban areas. Otherwise, the future looks dire:
"With the annual number of births projected to continue increasing in London, the absolute health burden will increase at the population level, unless air quality in London improves."
So, not only do the high numbers of fast-driving cars on our streets and highways kill humans at shocking rates, but now we have evidence of their poisonous effect on humans, even before they're out of the womb. Surely it's time to take Lloyd's suggestion to ban cars seriously. They do not belong in our cities.