Sleeping with the enemy: indoor airborne contaminants.

Apr 28, 2009

Gale RW, WL Cranor, DA Alvarez, JN Huckins, JD Petty and GL Robertson. Semivolatile organic compounds in residential air along the Arizona – Mexico border. Environmental Science and Technology doi: 10.1021/es803482u.

Synopsis by Heather Hamlin and Wendy Hessler


Sean Dreilinger/fickr
New research studying household air in homes in Arizona found more than 400 chemicals ranging from pesticides to phthalates, confirming that indoor air can be heavily contaminated with pollutants.

Pesticides, including diazinon, chlorpyrifos and DDT were found at surprisingly high levels, as were phthalates.



Understanding the health effects of exposure to common household chemicals has been difficult due to lack of information regarding what chemicals are present in homes and at what concentrations. Without this information, scientists can’t begin to make links between health problems and specific chemicals or mixtures of these chemicals.

Responses to chemical mixtures are often very different from responses to individual chemicals. And the differences are not well understood. For example, a mixture of several chemicals might be more or less severe than what we would predict from adding up the effects of individual chemicals (Laetz et al. 2009).

Chemical levels are likely to be much higher indoors than outdoors. This is due to decreased ventilation, slower chemical breakdown and other factors.

Household pesticides are a particular health concern. Pesticides can sometimes affect animals and people in similar ways as they affect insects and other pests they are intended to control. Due to these common, detrimental effects, many types – especially those that target the nervous system – have been banned from indoor use in the US and elsewhere.

Both diazinon and chlorpyrifos damage the nervous system of their intended insect targets and have been banned from indoor use.

Diazinon is an organophosphate pesticide formerly used indoors to control common insects such as cockroaches, ants and fleas. In the US, products containing diazinon for household use were outlawed in 2004, although it is still legal to use this chemical if it was purchased prior to the ban.

Chlorpyrifos, currently one of the world’s leading agricultural pesticides, is used to control insects. Although banned for household use, it is still widely used in agriculture on many crops including cotton, nuts, corn and fruit. Because of its widespread use, the US Environmental Protection Agency estimates that about 700 crops grown for food have been exposed to the pesticide (US EPA 2006).

DDT is another organophosphate pesticide used primarily to control mosquitoes, especially in tropical parts of the world. It is also widely known for its negative health effects. DDT can act like estrogen and has been show to affect many aspects of reproduction and development.

In wildlife, DDT has been associated with egg shell thinning, genital malformations and reproductive impairment. In humans, DDT has been associated with pancreatic cancer, non-Hodgkin’s lymphoma, breast cancer, impaired breast feeding and other health effects (reviewed by Longnecker et al. 1997).

DDT has been banned for use in the US and other countries. In 1997, Mexico pledged to phase out DDT use within 10 years.

Phthalates are a group of chemicals widely used in plastics, personal care products (i.e. cosmetics, soaps, shampoo and many fragranced products). Phthalate chemicals can be absorbed through the skin. They have been shown to interfere with reproduction and development. Phthalates are also associated with genital anomalies in male infants (Swan et al. 2005).

What did they do?

Researchers placed air collecting devices in 52 homes located in Arizona near the Mexico border. The samplers were put in various locations in the homes (kitchen, bathroom, living room, etc.) for 30 days. 

Gas chromatography was used to identify individual chemicals in the air samples.

To confirm the measures, samples from 12 of the homes were further analyzed by gas chromatography-mass spectrometry (GC-MS). GC-MS is a highly sensitive method used to determine what and how much of a chemical is present in a sample. It is considered to be the “gold standard” in scientific analysis.

The analysis machines were configured to detect organochlorine pesticides, but other chemical groups of interest included polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and phthalates.

A total of 586 individual chemicals were identified. The pesticides diazinon and chlorpyrifos were found in the greatest amounts and both were found in all of the 52 homes tested.

Twenty-seven different organochlorine pesticides were detected. p,p’-DDE, a breakdown product of the now banned pesticide DDT, was detected in more than 90 percent of homes.

Amounts of PCBs were generally low but were found in more than half the houses. They were detected in 56 percent of the 52 homes studied.

Phthalate chemicals were found at very large concentrations in indoor air.

Researchers were not able to identify at least 120 of the chemicals. Many of these unidentified chemicals had structures similar to fragrance compounds. Fragrances made up the major chemical component of the collected chemicals.

What does it mean?

Since so many different types of chemicals were detected in the indoor air samples, the results point to a high potential for exposure to pesticides and other harmful chemicals in household air.

While not all of the chemicals could be identified, those that were represent a mix of chemical types. Animal studies and some human research have found various health effects from exposure to the chemicals found in the air. Long-term exposure to the individual compounds or the mixture could have potentially harmful health effects.

The results also indicate that people who live in these homes are routinely exposed to this potentially harmful mix of chemicals. It is likely this type of exposure is common and widespread in homes throughout the US.

The United States banned the household use of diazinon and chlorpyrifos several years ago. Despite this, these pesticides were detected at greater concentrations than other pesticides. Chlorpyrifos, though, is still used extensively in agriculture. The study highlights a need for identifying the sources of these pesticides in indoor air.

High levels of DDT and its breakdown products are also indicative of continued use in or near the residences. Although the use of DDT has been banned in the US and is being phased out in Mexico, the authors note that it continues to be used along the US border.

The main human exposure to phthalates is thought to be through direct contact with skin through personal care products (cosmetics, perfumes, etc.) or directly through medical tubes and devices. Following direct contact, phthalates travel through the skin or mouth and have been found at high concentrations in human plasma and urine (Swan et al. 2005).

This study supports prior studies that reveal people can be exposed to phthalates through dust and air. The high concentrations of phthalates found in indoor air indicate that breathing in the chemicals could be a significant route of exposure. Studies that have measured phthalates indoors have also linked those indoor air levels with asthma and possibly higher rates of autism in children who live with certain types of vinyl flooring that contains phthalates.

Detailed information about the houses and the residents was missing from the study. Additional facts – such as whether residents smoked in the home, whether the homes were air conditioned or whether the homes were ventilated through open windows – could be useful when trying to identify the sources of the chemicals.

In general, this study raises awareness of the types and amounts of chemicals present in indoor air. It is a first step in understanding the links between indoor chemical exposure and health problems that may result from the long-term exposures.


Bornehag CG, J Sundell, CJ Weschler, T Sigsgaard T, B Lundgren, M Hasselgren, L Hägerhed-Engman. 2004. The association between asthma and allergic symptoms in children and phthalates in house dust: a nested case-control study. Environmental Health Perspectives. 2004 Oct;112(14):1393-7.

Laetz, CA, DH Baldwin, TK Collier, V Hebert, JD Stark and NL Scholz. 2009. The synergistic toxicity of pesticide mixtures: implications for risk assessment and the conservation of endangered Pacific salmon. Environmental Health Perspectives doi: 10.1289/ehp.0800096.

Longnecker MP, WJ Rogan and G Lucier. 1997. The human health effects of DDT (dichlorodiphenyl-trichloroethane) and PCBs (polychlorinated biphenyls) and an overview of organochlorines in public health. Annual Review of Public Health 18: 211-244.

Swan SH, KM Main, F Liu, SL Stewart, RL Kruse, AM Calafat, CS Mao, JB Redmon, CL Ternand, S Sullivan, JL Teague and the Study for Future Families Research Team, 2005. Decrease in anogenital distance among male infants with prenatal phthalate exposure. Environmental Health Perspectives 113: 1056-1061.

US EPA, 2006. Interim reregistration eligibility decision for chlorpyrifos.




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