Environmental Toxins and Female Reproduction

Michelle L. Matthews, M.D.
Assistant Director Reproductive Endocrinology and Infertility
Carolinas Medical Center

Introduction

There is increasing public interest regarding pollution and its effects on the environment as well as on human health and fertility. There is evidence that some environmental pollutants have effects on humans including links with suppression of the immune system, reproductive health, fatigue, weight loss, and possibly some forms of cancer if exposed in excessive doses. Due to these adverse effects on health there has been stricter regulation over industries that produce these substances. The effect of environmental pollutants on fertility has not been as clearly defined as other effects on health.

Toxins may affect many aspects of reproduction including sperm counts in men as well as hormonal levels, ovulation and oocyte (egg) quality in women. Human reproduction is such a complex process that it is difficult to isolate the extent to which a specific environmental toxin may influence human fertility. There are certainly many important factors to consider when evaluating an individual's risk of significant toxin exposure including the dose, duration, and timing of exposure. Several other factors including age, genetics, nutritional and health status also may influence susceptibility to toxins. For these reasons it has been difficult to adequately study the effects of environmental toxins on human reproduction. Most research has focused on studies in animals and anecdotal reports. Studies done on animals are somewhat difficult to apply to humans particularly because the dosages used are often higher than those at which humans may be exposed in the environment. In addition, there are substantial variations in the degree of toxin exposure between individuals depending on the occupation of the individual, dietary factors, and the degree of pollution in the local environment.

There are three general categories of environmental toxins: pesticides/fungicides, heavy metals, and industrial pollutants. Some pesticides and fungicides used in agriculture have been shown to be toxic to mouse oocytes in excessive dosages. Metals such as lead and mercury have also caused oocyte abnormalities. Some industrial pollutants produced as a byproduct of combustion and chemical production have also been shown to be toxic. Unfortunately, these chemicals have been shown to persist in the environment for years after their production. They may be inhaled or ingested by humans and are retained in the human body for years. Levels of these chemicals have been measured in the human body and have been isolated from the follicular fluid of the female ovary. Therefore, human oocytes may be directly exposed to industrial pollutants at least in low levels. The exact impact on human fertility is difficult to determine but many of these chemicals have been shown to be harmful to animal reproduction. There is no definitive evidence that routine levels of exposure to these agents through the air and food supply significantly impacts human fertility.

Women working in specific occupations may have an increased risk of infertility due to excessive exposure to certain toxins. Some studies have shown an increased risk of infertility in women exposed to anesthetic gases such as dental assistants, anesthetists and nurses. Also, beauticians and women working in the textile, rubber, and dry-cleaning industries may have an increased risk of infertility from the chemicals used in these processes. The exact risk has not been clearly defined. It is important to note that these are anecdotal reports and not well designed research studies. In fact, most women working in these professions do not experience infertility and there are no recommendations for women experiencing infertility to stopping working in these occupations.

In conclusion, more research needs to be performed to determine the specific impact of toxins on female fertility. Women in certain occupations with exposure to specific substances may be at a higher risk of infertility although this is controversial and should be viewed with caution. Environmental pollutants are clearly a health concern and some preliminary evidence suggests that excessive exposure could potentially contribute to some fertility related issues. There is currently no evidence that everyday exposure to most agents in our environment is a significant detriment to fertility. Hopefully, increasing public interest and awareness about these toxins will prompt further investigation into the impact of these agents on fertility.