Researchers at the University of Naples in Naples, Italy studied 85 young and middle-aged men who worked in highway tollbooths and compared them to 85 men of the same age living in the same area, but who held other kinds of jobs. The toll both workers were exposed to vehicle gasses an average of six hours a day. Blood and sperm samples were collected from all the study participants.
Testosterone, follicle stimulating hormone and luteinizing hormone -- all critical in proper sperm function -- were found to be within normal range in both groups of men, researchers report in the May issue of Human Reproduction.
However, the tollgate workers showed a greater concentration of inactive sperm with sperm movement being significantly lower when compared to the men who did not work in tollbooths.
Blood samples showed that, while blood lead levels were not as severe among tollgate workers as those in found in previous research looking at factory employees, the toll booth employees still carried enough lead in their bodies to impair sperm function. Researchers also found evidence of nitrogen oxide, a major pollutant from vehicle emissions, and a top suspect behind the sperm damage.
"Environmental levels of occupational pollutants, except carbon dioxide, at the tollgates, exceeded the maximum legal levels and the workers were exposed to significantly higher levels of nitrogen oxides, sulphur oxides, carbon monoxide and lead," said lead researcher Dr. Michele De Rosa in a statement. "The sperm count did not differ significantly between our study group and the controls but, in general, the sperm of the study group was more feeble and less active so it has a lower fertility potential." De Rosa did not return repeated requests for an interview.
Previous research conducted in both the United States and abroad has linked male infertility to lead exposure. Many studies have looked at men who worked in factories and farms, occupations that frequently involve exposure to industrial solvents, and found associations between environmental toxins and impaired sperm function. This is one of the first studies to look at men who worked in highway tollbooths.
"Whether this applies to other workers dealing with automobiles, I supposed that would seem like a logical progression, but it would have to be studied," said Dr. Ronald Swerdloff, a professor of medicine specializing in male infertility and chief of endocrinology at Harbor-University of California at Los Angeles Medical Center in Los Angeles. "There are a lot of substances produced as a result of engine-type pollution. It seems reasonable to think they might have been exposed to increased exhaustion from the engine," he told United Press International.
Swerdloff suggested it's possible the body may be preventing defective sperm from fertilizing an egg.
"This is an interesting observation that I think fits in with concerns in many places in the world in which there are environmental toxins that will affect fertility," Swerdloff said. "In some ways, this may be a protective mechanism in identifying sperm damaged from pollutants."
John Peterson Myers, an environmental health scientist and chairman of the Science Communication Network in Washington, D.C., called the findings "really interesting."
"What's happening is that we are in the midst of a revolution in understanding environmental exposures and their risks to health," Myers told UPI. "People are being affected in ways we did not expect before."
Myers added, "It's difficult to be certain about cause and effect. I have not heard of one (study) before looking at exposure, in essence, to car emissions. It doesn't surprise me, but it's a new and important result."
These results also suggest it would be interesting, Myers said, to investigate whether park rangers in national parks were being affected by vehicle emissions since vehicle pollution has been a major problem in these designated lands.
(Reported by Katrina Woznicki, UPI Science News, in Washington)
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