A common pesticide used to spray lawns and golf courses often ends up in the semen of the men who spray it, according to a new Health Canada study.

2,4-D has been used for almost 40 years.

According to a study of 97 male Ontario farmers, about half had detectable levels of pesticide.

The study's authors express concern about pesticides in semen because there's a possibility the chemicals could end up in the fetus. But they emphasize that the levels of 2, 4-D found were "trace levels."

In the summary, the report says "it is crucial to understand the relationship between pesticide-handling practices, the presence and levels of pesticide residues in semen and the risk of adverse reproductive outcomes."

The study is published in a research journal Reproductive Toxicity.

2,4-D kills weeds without affecting grass

2,4-D kills broad-leafed plants, but not grass. It's the major active ingredient in weed killers such as Killex, Trillion and Par-3. It's also often mixed two other weed killers, dicamba and mecoprop.

A separate study of farmers in Argentina had different results, for the worse. Their 2,4-D levels were as much as 300 times higher than those of Ontario men. The men in Argentina also had significant damage to their sperm cells.

The findings aren't conclusive. Other studies have said sperm damage once caused by 2,4-D-based pesticides was caused by dioxins that crept in as accidental contaminants.

The industry says those early years of contaminated 2,4-D are history and there's no dioxin in today's weedkillers.

A 1997 study by the U.S. Environmental Protection Agency concluded 2,4-D is "non-carcinogenic, non-teratogenic (does not cause birth defects) and non-mutagenic."