Cumulative effect of chemicals on male reproductive system measured at Animal Reproduction and Biotechnology Laboratory
February 6, 2008
Common household chemicals and widespread pollutants are changing male reproductive health and impacting sexual function, development and cancer rates of today's generations and possibly their offspring, according to more than 15 years of research by a Colorado State University expert. For example, one study looking at sperm counts globally from 1940 - when chemicals first began to be widely produced - to the 1990s, indicates a 1.15 percent per year decline in sperm counts. These declines may be linked to chemical exposure.
Impaired sperm quality and impotence
Rao Veeramachaneni, a biomedical sciences professor in the College of Veterinary Medicine and Biomedical Sciences, has found that chemicals including insecticides; pesticides; common pollutants in ground water; and chemicals in plastics, make-up and nail polish are on a growing list of culprits causing developmental abnormalities such as hypospadias and cryptorchidism, impaired sperm quality and impotence. Reproductive health can be compromised if males are exposed at various times in life spanning from in utero up to adulthood.
Veeramachaneni's findings span the globe and are across species lines, from humans to horses, wildlife to frogs. His research, coupled with the collective findings of other experts in the field, indicates a strong link related to pollutants, and incidence of such impacts continues to increase from year to year as chemicals infiltrate the modern world.
Trends show lasting effects of chemicals
"Exposure to these chemicals, particularly during certain windows of time during fetal development, in newborns or as adolescents, can do permanent damage," said Veeramachaneni. "It's been a difficult task to trace the impact of these chemicals because an exposure as a fetus may not be manifested until that fetus becomes an adult. Once exposed, many males develop a condition for life. But when we look at the big picture -- at trends over time -- research shows lasting effects of chemicals since their popularity after World War II."
Some of these chemicals can survive in the environment for 30 to 40 years, and the chances for exposure are high because the chemicals have permeated our world. For example, the EPA says that about one-third of the nation's lakes and one quarter of its rivers are polluted. There is also evidence that exposure today to some of these chemicals can affect the reproductive health of this generation as well as the future health of offspring of those exposed. The incidence of testicular cancer in young men 15 to 35 years old has increased three to four fold over the past 50 years, particularly in the Western world.
Increasing incidence of reproductive systems abnormalities
These chemicals affect the body through several channels. They attach to receptors in the body that help hormones carry out their functions and either block actual hormones from attaching or mimic the expression of the real hormones, causing confusion in the male body. In addition, some interfere with the body's natural production of hormones.
A pattern emerges when comparing the explosion of the world's use of chemicals, including pesticides and herbicides, and the steadily increasing incidence of testicular cancer, reproductive system abnormalities and impotence.
- Phthalates, which are used in a variety of products including cosmetics, upholstery, pharmaceuticals and medical tubing, and also are found in drinking water and air. The chemicals can be found in body fluids of people who have been exposed, including in urine, blood and breast milk. Presence in breast milk can pass exposure on to an infant.
In a series of studies funded by the Environmental Protection Agency, Veeramachaneni's laboratory found that exposing tadpoles to dibutyl phthalate, one form of phthalate, drastically slows their growth and reproductive development. At varying doses, tadpoles lagged weeks behind non-exposed frogs in developing legs and entering adulthood. More significant, however, was the impact on their ability to reproduce; one effect of the chemicals is particularly notable on their mating calls. Those exposed to chemicals had calls that were weaker and shorter. Images of the larynx, the voice box, showed that it was significantly underdeveloped. Without a competitive mating call, the frogs will not be able to reproduce successfully. Participants in these studies include Colorado State graduate students Ty Higuchi, Shannon Lee and Gwen Owens.
- DDT and other pesticides, and herbicides have been linked to testicular cancer in humans and animals. Reflecting human trends in the U.S. and abroad, in collaboration with medical scientists at University of Pretoria, South Africa, Veeramachaneni has found instances of testicular cancer in wildlife in Africa, potentially tied to the increasing renewed use of DDT to fight malaria-carrying mosquitoes. His research showed that DDT causes precancerous lesions in the testis. Veeramachaneni also documented cancerous lesions in the testes of infertile domestic horses and wild deer, and is working on a possible connection to ubiquitous pollutants.
- The incidences of hypospadias and cryptorchidism are increasing. While figures indicating the increase vary by population, the Centers for Disease Control and Prevention cites a marked twofold increase in the last 25 to 30 years, now impacting almost one per 100 males born. Hypospadias can affect urination and sexual function. Veeramachaneni's laboratory has found that exposure to some chemicals such as phthalates causes hypospadias and cryptorchidism.
- Historical studies show that the quality of sperm in humans has decreased rapidly in the last 50 years. With the assistance of research associate Carol Moeller, Veeramachaneni's electron microscopic studies show that sperm quality is affected by malformations of structures that are needed for fertilization of the egg or two or more sperm attached to each other following exposure to a variety of so-called innocuous chemicals.
- Erectile dysfunction is reported in one-third of the U.S. male population. It also is being linked to chemicals in the environment. Vinclozolin, a fungicide commonly used in agriculture, can contaminate food and water supplies. In laboratory tests, Veeramachaneni and his research associate, Jennifer Palmer, found that some male offspring of animals exposed to vinclozolin during pregnancy displayed a complete lack of interest in females.
- Learn more about the Animal Reproduction and Biotechnology Laboratory at http://www.cvmbs.colostate.edu/bms/ARBL/arbl_overview.htm.
- Visit Professor Veeramachaneni online at http://www.cvmbs.colostate.edu/bms/veeramac.htm.
Contact: Dell Rae Moellenberg
Phone Number: (970) 491-6009