Research Note 94-10 - Indoor concentrations of phthalaates and PAHs

No. 94-10
June 1994
California Environmental Protection Agency Brief Reports to the Scientific and Technical
Air Resources Board Community

Research Division, John R. Holmes, Ph.D., Chief P.O. Box 2815, Sacramento CA 98512

Indoor Air Concentrations
of Phthalates and PAHs
in Southern California Homes

This study was the first to measure indoor air levels of phthalates and polycyclic aromatic hydrocarbons (PAHs) in a large representative sample of homes. Phthalates, which are commonly used plasticizers, and PAHs, which are combustion byproducts, are toxic air pollutants. Several phthalates are known to cause birth defects in animals, and many PAHs are known or suspected carcinogens. Both groups of compounds are emitted from a number of indoor sources. Measurements were made in 125 homes in the fall of 1990 in Riverside. Indoor concentrations of phthalates were, on average, about 2 to 15 times higher than outdoor concentrations. Average indoor PAH levels ranged from about one-half to two times average outdoor levels, and levels were higher in homes in which cigarettes were smoked. This study was performed by Research Triangle Institute.


The goal of ARB's Indoor Air Quality/Personal Exposure Assessment Program is to identify and reduce people's indoor exposures to air pollutants. Phthalates and PAHs are two large groups of toxic air pollutants with a number of indoor sources. Prior to this study, little was known about indoor levels of these pollutants.

Many phthalates and PAHs (as part of polycyclic organic matter) were recently identified by the Air Resources Board as toxic air contaminants. They are also listed as federal hazardous air pollutants. Several phthalates have been shown to cause birth defects in laboratory animals. Many of the PAHs, including benzo(a)pyrene, are known to cause cancer or genetic damage. Phthalates are commonly used plasticizers that are likely to be present in many plastic items found in indoor environments. PAHs result from combustion processes; indoor sources of PAHs include smoke from cigarettes, from wood burning, and from the grilling or frying of food.

This study was performed in conjunction with a larger U.S. EPA project, the Particle Total Exposure Assessment Methodology Study (PTEAM). The primary objective of PTEAM was to measure people's actual exposure to particles. ARB co-funding allowed for simultaneous monitoring of additional pollutants at reduced cost and ensured that the project was conducted in California.
Methods: In this study, the investigators measured both particle-phase and vapor-phase phthalates and PAHs inside 125 homes in Riverside, California. Concurrent outdoor sampling was conducted at approximately one-half of the homes. The 125 homes were a subset of the 178 homes monitored in the main PTEAM project. Each home was monitored for two consecutive day/night 12-hour periods during the fall of 1990. Cartridges containing a quartz fiber filter (to collect the particle-phase compounds) followed by an organic resin (to collect the vapor phase compounds) were used to collect the phthalate and PAH samples. The samples were subsequently extracted, then analyzed by gas chromatography/mass spectrometry.
Results: Indoor and outdoor concentration measurements were obtained for five phthalates and twelve PAHs. The following table highlights some of the results for selected compounds:

Average Residential Concentrations
of Selected Phthalates and PAHs

*NQ=Not quantifiable

Except for di-n-octylphthalate, all of the phthalates were virtually ubiquitous in indoor samples. Phthalates were not as commonly detected in outdoor samples. Median indoor levels (excluding di-n-octylphthalate) ranged from about 2 to 15 times outdoor levels. This indicates that the predominant sources of phthalates are indoors. Concentrations of individual phthalates generally did not correlate well with each other, suggesting different sources.

Generally, PAHs were detected in most of the indoor and outdoor samples. Median indoor levels ranged from about one-half to two times outdoor levels. Average PAH levels ranged up to three times higher in homes in which cigarettes were smoked than in non-smokers' homes. Outdoor levels of PAHs tended to be higher in the nighttime than in the daytime. The investigators surmised that this may have been due to greater dispersal or photodegradation of the PAHs in the daytime. In both indoor and outdoor samples, levels of individual PAHs generally correlated well with each other, suggesting one or more common sources. Those correlations among individual PAHs tended to be higher outdoors than indoors.
Significance and Application: This study was the first to measure indoor levels of phthalates and PAHs in a large representative sample of homes. The data obtained by this work will improve estimates of Californians' exposures to phthalates and PAHs and enable ARB staff to provide better guidance to the public regarding pollutant sources in their homes.
Related Projects: This study was conducted in conjunction with a larger U.S. EPA project, the Particle Total Exposure Assessment Methodology Study (PTEAM). One of the main results from that project was that residential indoor and outdoor levels of particles were about equal on average, but daytime personal exposures were about 50 percent greater than either indoor or outdoor residential concentrations. The causes of the higher personal exposure levels of particles have not been completely determined, but the higher levels are believed to have resulted from individuals generating particles with their activities, such as cooking and housecleaning. The report for the main PTEAM study is available from the National Technical Information Service (Particle Total Exposure Assessment Methodology (PTEAM): Riverside, California, Pilot Study - Volume 1; order number PB93-166957).

A related ARB field study was conducted to obtain information on the levels of PAHs and carbon monoxide inside homes with different combustion sources (cigarette smoking, fireplaces, woodstoves, and gas heaters) and the relative emission strengths of those sources. That study was conducted in the winter of 1991-92 in 280 homes located in northern California. Combined with the information obtained from PTEAM, the findings will enable ARB staff to estimate Californians' indoor exposures to PAHs and will contribute to the development of effective measures to reduce those exposures.

This research was conducted under contract with Research Triangle Institute (ARB contract no. A933-144). Comments or questions can be directed to Peggy Jenkins by mail, FAX (916) 322-4357, phone (916) 323-1504, or e-mail.
Copies of the research report upon which this Note is based can be ordered from:
National Technical Information Service
5285 Port Royal Rd
Springfield VA 22161
Request NTIS No. PB93-205649
Title: PTEAM: Monitoring of Phthalates and PAHs in Indoor and Outdoor Air Samples in Riverside California, Volume 2
Authors: L. Sheldon, A. Clayton, J. Keever, R. Perritt and D. Whitaker