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Birth Defect Information - Exposures and Risk Factors (Air Pollution)

MO-08-0077 CBDMP


4 Common Air Pollutants

  • Carbon monoxide – found in car exhaust and industrial emissions, as well as in cigarette smoke. It interferes with the blood’s ability to absorb and transport oxygen.
  • Ozone – a byproduct created when other pollutants react in sunny conditions.
  • Nitrogen dioxide – forms when automobile and industrial emissions combine with oxygen.
  • Particulate matter – created by combustion from automobiles and industry as well as mechanical processes, such as tire wear.
  • What effects do air pollutants have on pregnancy and birth defects?

    In a study done by the UCLA School of Public Health using CBDMP Registry data, it was found that the risk of birth defects increased among women exposed to elevated amounts of ozone and carbon monoxide in the second month of pregnancy.1 The second month of pregnancy is when significant heart and organ development occurs. Therefore, it is not surprising to find that women who are exposed to high levels of these two pollutants may have an increased risk of having a child born with a heart defect. The study found that some of these heart defects were conotruncal heart defect, pulmonary artery/valve defect and aortic artery/valve defect. The study did not take into account other prenatal exposures such as smoking, vitamin use and maternal health.

    Studies have also found that pregnant women exposed to high levels of nitrogen dioxide, carbon monoxide and particulate matter are at an increased risk of experiencing restricted fetal growth (intra-uterine growth restriction).2,3

    An association between air pollution and birth defects is biologically plausible. One must remember that other environmental and risk factors must be considered and are difficult to rule out during research studies. Some of these may include smoking, maternal health as well as behaviors and other exposures that may be encountered at work and/or during extracurricular activities.


    1. Ritz B, Yu F, Fruin S, Chapa G, Shaw GM, Harris JA. (2002). Ambient air pollution and risk of birth defects in Southern California. American Journal of Epidemiology Jan 1;155(1):17-25
    2. Chen, J. (2009, 01 31). Birth defects soar due to pollution. Retrieved May 26, 2009, from China Daily Web site: http://www.chinadaily.com.cn/china/2009-01/31/content_7433211.htm
    3. Preidt, R. (2009, 04 09). Air pollution exposure may slow fetal growth. Retrieved May 26, 2009, from MedicineNet.com Web site: http://www.medicinenet.com/script/main/art.asp?articlekey=99230
    Last modified on: 9/1/2009 1:40 PM