Are Human Sperm Counts Going Down?

There is a controversy in the scientific world about sperm. A 1992 study from Denmark came to the conclusion that sperm counts have gone down about1% per year for the past 50 years. Many other studies were launched inreaction to it, some of which dispute these claims and question the accuracyof the study's methods.

Some environmentalists blame this decrease in sperm count on the generalincrease in pollutants such as pesticides, plastics, nuclear waste, anddetergents. They point to evidence of reduced fertility in chemical andnuclear plant workers, and the fertility problems of many members of theanimal kingdom that have been linked to environmental chemicals. There also seems to be a correlation between the amount of pollution in an area and sperm counts among males that live there.

Chemical companies have launched their own studies which (surprise!) findthat these claims are exaggerated. One chemical industry sponsored studyclaims that iodized salt is the real culprit.

While I am generally suspicious of studies sponsored by industries that havea financial interest in keeping their controversial products on the market,it's difficult to be certain that the statistics quoted in any of thesesperm count studies are correct. Results can be skewed by how the samplesare taken, where the subjects live, and many other factors. The long periodof time covered adds further room for error.

While I believe there are many other compelling reasons to decrease theamount of pollutants put into our environment, it is hard to ascertain ifthis problem is directly affecting human fertility and if so, to what extent.

The debate continues. Are sperm counts really going down? If so, is it too late to do anything about it?

General Resources:

Semen Quality and Male Reproductive Health: The ControversyAbout Human Sperm Concentration Decline  (cached)
An abstract of an article that says the debate whether sperm counts havegone down or not is still open.

Resources that say sperm counts HAVE gone down:

Evidence for Decreasing Quality of Semen During Past 50Years  (cached)
An abstract of the 1992 article by Carlsen et al that fueled much of thedebate on decreasing sperm counts.

Have Sperm Densities Declined? A Reanalysis Of Global TrendData  (cached)
An abstract of a study that reanalyzes the data in the 1992 study above.The findings were that sperm densities have declined in North America andEurope (with regional variations) but not in "non-Western" countries.

Masculinity at Risk  (cached)
An article that describes the sperm count controversy and explains some ofthe difficulties in measuring sperm counts over time.

They Can Sow But Canˆ¢t Reap: The Demise of HumanSperm  (cached)
An article by John Robbins, defending what he wrote on theissue in his book Diet For a New America.

Resources that say sperm counts HAVE NOT gone down:

Have sperm counts deteriorated over the past 20 years inhealthy, young Japanese men? Results from the Sapporo area  (cached)
A 20 year study in Japan that showed no decline in sperm counts among theparticipants.

Sperm Counts Unchanged over 50 years  (cached)
A press release about a University of Southern California study that refutesthe idea that sperm counts have gone down. This study only looked at men inthe Los Angeles area who were partners of women seeking fertilitytreatment.

Sperm Counts and Infertility  (cached)
Another article that says it's not possible to conclude that sperm countshave gone down. From a site that is run by the Canadian Chemical ProducersAssociation.

Have sperm counts been reduced 50 percent in 50 years? Astatistical model revisited  (cached)
An article that refutes the 1992 study listed above. The authors wereworking for the Dow Chemical company at the time of this study.

Resources about the reasons for sperm count decline:

Environmental Estrogens: Fact or Fiction?  (cached)
An article about "environmental estrogens" (a type of chemical that affectsthe hormone estrogen in men and women) that refutes the idea that thesechemicals are causing breast cancer and fertility problems. This comes fromanorganization that is funded by and often defends chemical, petroleum, andnuclear industry interests.

Down for the Count  (cached)
An article from Mother Jones magazine (which leans towards theenvironmental movement) that maintains that environmental estrogens areindeed a major problem.

Chemicalsand Male Reproduction  (cached)
An article with findings from the National Institute of Environmental HealthSciences (a government agency) that suggests environmental chemicals arehaving an impact on male fertility. This article also explores issues ofincreasing animal infertility.

Environmental and Occupational Hazards and Maleinfertility  (cached)
Describes various environmental and workplace issues that may be responsiblefor low sperm count including heat, radiation, metals, estrogens,pesticides, solvents, and drugs.

The Science of Sperm Count Declines  (cached)
An article that describes the sperm count controversy and explores thetheory that pollutants do their damage to males while they are still intheir mothers' wombs.

Sperm Count Fall Blamed on Salt  (cached)
An article about a study that points to iodized salt as a reason for spermcount decline. The scientists who did this study also were working for theDow Chemical Company.

Nutrasweet Lowers Sperm Counts
a Japanese study found that Aspartame (aka Nutrasweet) may lower sperm counts.