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10.08.2015

Exhaust fumes lower testosterone levels

If you're on the road a lot and breathe in exhaust fumes, it could be that it's having a negative effect on your testosterone level. An animal study done at National Taiwan University has shown that male rats that breathed in exhaust gases from motorbikes and scooters started to produce less testosterone because the fumes caused damage to their testes.

Study
In Taiwan nearly everyone rides a motorbike or scooter. The researchers wanted to know whether exhaust fumes have a negative effect on the sexual organs. It has long been known that diesel fumes are harmful, but not much is known about the exhaust fumes from motorbikes.

So the researchers exposed male rats for four weeks to gases produced by the old motorbike of one of the young researchers: a 1992 Yamaha Cabin. The Taiwanese kept the motor running, collected the gases and then blew them into the rats' cage. The rats got to breathe the gases in between nine and ten every morning and between four and five every afternoon, from Monday to Friday.

Results
The rats in some of the experiments lost weight as a result of exposure to fumes, losing nine percent of their bodyweight. Their sperm count also decreased and when the researchers put the male rats together with sexually receptive females, less mating took place than normal. Exposure to fumes reduced mating by sixty percent. And when the animals did mate, fewer females became pregnant or they produced fewer offspring.

The exhaust fumes lowered the concentration of testosterone in the blood by seventy percent. But when the rats were given extra vitamin E in their food, then the decrease was much less: only forty percent, as the figure below shows.

ME = motorbike exhaust fumes.

The testes suffered most damage from the exhaust fumes, other organs were not affected. "Motorcycle exhaust had no effects on the relative weights of liver, kidney, lung, spleen, seminal vesicles, ventral prostate, adrenal, and thyroid", the Taiwanese wrote.

The amount of free radicals in the testes' cells increased. The concentration of the protective enzyme superoxide dismutase almost halved, and the synthesis of the inflammatory protein interleukine-6 increased.

Vitamin E supplementation also completely blocked the increase in interleukine-6. It seems that this anti-oxidant vitamin protects the testes against exhaust fumes and also helps keep up sperm production, as the figure below shows.

Source:
Toxicol Sci. 2008 May;103(1):137-48.