Two of the larger reproductive health enigmas in recent years have been guy things. Namely mysterious declines in sperm counts around the globe and a relatively sudden downturn in the numbers of boys being born in certain parts of the world. Last month, two new studies shed some possible light on these phenomena, and both link the evidence at hand to toxins in the environment.
At the Washington State Department of Health, researchers analyzing department birth data found that men who worked in the flour industry tended to produce fewer baby boys than men in the general population. Out of 59 children born between 1980 and 2002 to families whose fathers were employed in flour mills only 22, or 37%, were male. The study also found that these baby boys weighed an average of 12 ounces less than their peers.
The data contrasts markedly with male birth rates in Washington state as a whole, which during the same period averaged slightly more than 51%. Scientists aren’t quite sure what’s responsible for the discrepancy but suspect it has something to do with the pesticides to which mill workers are routinely exposed. Flour mills use a variety of chemicals to control insects in their facilities. One pesticide, a compound called DBCP, has already been banned due to its negative effects on male fertility and birth rates.
When undisturbed, nature tends to produce slightly more boys than girls in the human species; for every 100 female births there will be about 105 male births. It’s a gap that statistics show has been narrowing in recent decades. In 2001, there were 104.6 male births per 100 female births, down from a figure of 105.5 recorded in 1970. As with the mill workers, scientists theorize that environmental pollutants may be responsible for the decline.
The second study to surface last month offered intriguing clues into another male-related mystery: the decline of sperm counts in the modern world. This project used the data from the city of Seveso, Italy, site of one the world’s greatest dioxin disasters.
On the afternoon of Saturday July 10, 1976, a broken valve at the Industrie Chimiche Meda Societa Azionaria chemical plant in Seveso released as much as 44 lbs. of dioxins into the sky. The poisonous cloud that settled over the town’s residents inadvertently created a terrible uncontrolled experiment in dioxin contamination.
For years, scientists have studied the population of Seveso in an attempt to understand dioxin’s effects on the human body. Indeed, much of what we know today about this most toxic of all chemical pollutants comes from the 37,000 people who were exposed in the accident.
Now the latest evidence from Seveso has been released. Researchers seeking clues about dioxins effects on male fertility studied the sperm counts of 400 male volunteers who were babies, boys, or teenagers at the time of the disaster and compared their findings to a control group in the general population.
Tests showed that men who were between the ages of one and nine when they were exposed to Seveso’s dioxin cloud had sperm counts 43% lower than the control average. Men who were over 17 at the time of the incident showed no significant effect. Interestingly, in the group of men who were ten to 17 when the exposure occurred, sperm counts were 63% higher than the control groups.
Researchers said the results showed that there are sensitive windows of development during which time the male reproductive system can be permanently inhibited or stimulated by the hormonal effects dioxin exposures create in the human body. The findings also suggest that declining sperm counts worldwide may be a result of dioxin contamination in the general environment. If that’s true, scientists would expect to see sperm counts improve in the coming years as dioxin clean-up and prevention efforts begin to bear fruit.
What remains unknown is what level of dioxin exposure is needed to trigger the changes the study found and whether or not the average person’s typical exposure level crosses this crucial threshold. That makes it important to do whatever we can to keep this hazardous pollutant at bay. For more about dioxins and a list of things you can do to keep your family safe, read our special web feature on avoiding dioxins.