Reproductive Problems:  Chemicals Associated With Them and Exposure Assessment

Chemicals associated with adverse reproductive outcomes
Exposure assessment
   Being exposed to a reproductive toxicant and wanting to become/is already pregnant
   Being exposed and having a young infant at home
Proposition 65

The US Environmental Protection Agency (EPA) has indicated that numerous environmental agents including chemicals commonly found indoors (e.g. tobacco smoke, some pesticides, lead and heavy metals, alcohols, and plastic additives) are suspected of causing developmental toxicity in humans.^1,2 Endocrine disrupters such as pesticides and plasticizers, which affect the function of sex and thyroid hormones, present a new concern for reproductive toxicity. While the impact of reproductive effects from indoor environmental exposures is unknown, it could be significant. Approximately three percent of newborn children have one or more malformations at birth.

A known reproductive hazard is one for which extensive data from human beings indicate adverse effects at specific doses.³ However, toxicity data is scarce and there is no definitive list of reproductive toxins because of the limitations for studying human toxicity.⁴ Although there is no definitive list, it has been shown that alcoholic beverages, illicit drugs, cigarette smoke and therapeutic agents can possibly increase the risk of an adverse reproductive outcome. Along with the items listed, exposure to environmental and occupational toxins can have an adverse effect on reproduction. Since thalidomide use was found to be associated with limb reduction defects in Europe in the 1960s, there has been a growing interest in research of reproductive toxicants.⁴

Chemicals Associated With Adverse Reproductive Outcomes

Table 1 lists some examples for which human evidence exists.⁴

Table 1. Examples of chemicals associated with or suspected of adverse reproductive outcomes.

*Well documented to affect humans outside of a workplace or medical therapeutic setting
**Occurred in unique settings of high dose ingestion

In addition to these chemicals, there are hundreds others, including organic solvents and pesticides that have been shown to have adverse effects in animals.

Exposure Assessment

Whether a woman is pregnant, is thinking of becoming pregnant, or already has children, it is important to assess if she has been exposed to toxins in her home or workplace. A common misconception is that the mere presence of a toxic agent is synonymous with exposure and that any exposure to a known reproductive toxin suggests a high or even certain risk of an adverse effect. On the contrary, absorption into the body must occur for an adverse effect to be produced.^3,4

Being Exposed To A Reproductive Toxicant And Wanting To Become Or Is Already Pregnant (Or Is Fathering A Pregnancy)

• First, the type and amount of toxins present should be evaluated. If one works in a high-risk environment such as a medical institution, chemical plant, laboratory or any other occupation that would raise his/her potential risk of exposure, one should be able to refer to the MSDS for each chemical or substance with which he/she works. Although MSDS can provide information regarding some toxic effects, many have inadequate reproductive health data, fail to include the data, or do not give exposure limits to specifically protect against reproductive risks.³ For substances such as lead, mercury and PCBs, monitoring of blood levels for current exposure is very useful. Many times, blood levels can be lowered below the toxic range before conception. At this point, it would also be useful to talk with his/her employer and doctor. They can provide specific information to one's personal situation.

• In assessing exposure, there are several things to be considered:

  • Route of exposure (inhalation, ingestion, dermal)

  • Concentration in the medium

  • Duration of exposure

  • Other exposures to the same or similar acting agents from food, work, medications to name a few examples 

  • Relation to critical periods in embryogenesis

  • Protective equipment such as ventilation, masks or filters

• Next, one would need to avoid further exposure to the toxin(s). Remember, with the exception of high-dose situations involving an agent with known dose-response data, one is not commonly in a situation where an adverse outcome has truly become "likely." At home, it is equally important to reduce exposure to harmful chemicals and their fumes including household cleaners, pesticides and solvents. Every effort should be made to keep exposure to hazardous chemicals to a minimum throughout the pregnancy.

• Although it is possible to come into contact with hazardous chemicals on a daily basis, the vast majority of reproductive adversity is due to infections, older age at conception, and the natural errors of our genetic transmission system.⁴ Because of this, it is sometimes difficult for a clinician to declare with certainty that a toxin contributed to an adverse outcome.³

Being Exposed And Having A Young Infact At Home

If further exposure cannot be avoided, here are some things to consider:

• There are possible risks from exposure through breastfeeding or bringing toxic agents into the home. In the case of breastfeeding, a consulting physician should be able to determine if the benefits of breastfeeding outweigh the risks of chemical exposure.

• Many different chemical agents may be concentrated and/or excreted in breast milk, including chlorinated pesticides, PCBs, lead, mercury, and others.⁴

Proposition 65

In November of 1986, the state of California adopted Proposition 65 (also known as The Safe Drinking Water and Toxic Enforcement Act of 1986) in order to address growing concerns about exposures to toxic chemicals. Proposition 65 requires the listing of chemicals known or suspected of causing cancer, birth defects or other reproductive harm. This list contains over 400 carcinogens and over 200 reproductive toxicants. Reproductive toxicants are those agents that cause or are suspected of causing birth defects or other reproductive harm. The list is provided to allow California consumers to make informed choices about products they purchase and to enable residents or workers to take appropriate actions to protect themselves from exposure. The list contains many kinds of chemicals, including dyes, solvents, pesticides, drugs, food additives and byproducts of certain processes.⁵

This list, however, includes many chemicals that are only suspected of causing reproductive toxicity and can sometimes be confusing (see www.oehha.ca.gov/prop65/prop65_list/Newlist.html). Therefore, research remains of utmost importance to make sound policies and recommendations with respect to reproduction.

1. National Cancer Institute. Health effects of exposure to environmental tobacco smoke. Pub. # 99-4649, 1999.

2. US Environmental Protection Agency. Guidelines for developmental toxicity assessment. US Environmental Protection Agency, Washington DC. 1991.

3. Paul M. Occupational reproductive hazards. Lancet 1997;349:1385-8.

4. Kipen HM, Zuber C. Occupational and environmental impacts on reproductive health. Ann NY Acad Sci. 1994 Dec 30;736:58-73.

5. Chemicals Listed Effective August 4, 2000 as Known to the State of California to Cause Cancer. Updated 8/04/2000 www.oehha.ca.gov/prop65/prop65_list/Newlist.html.