Prepared for the California Air Resources Board and the California Environmental Protection Agency: California Air Resources Board Research Division 1001 I Street, 5th Floor Sacramento, CA 95814
Prepared by: William W Nazaroff (principal investigator), Beverly K. Coleman, Hugo Destaillats, Alfred T. Hodgson, De-Ling Liu, Melissa M. Lunden, Brett C. Singer, and Charles J. Weschler
Department of Civil and Environmental Engineering 661 Davis Hall University of California Berkeley, CA 94720-1710
Indoor Environment Department Environmental Energy Technologies Division Lawrence Berkeley National Laboratory 1 Cyclotron Road Berkeley, CA 94720
April 2006
Acknowledgments The authors thank Dorothy Shimer, Jeff Yanosky, and Peggy Jenkins of the Research Division of the Air Resources Board for their effective technical management of this project. We acknowledge, with thanks, the experimental contributions of Tosh Hotchi and Michal Landau.
This report was submitted in fulfillment of Contract 01-336, “Indoor air chemistry: Cleaning products, ozone and toxic air contaminants,” by the University of California, Berkeley, under the sponsorship of the California Air Resources Board. Work was completed as of 13 May 2006.
Abstract
When cleaning products and air fresheners are used indoors, occupants are exposed to airborne chemicals, potentially leading to health risks. Indoor air pollutant exposures owing to cleaning product and air freshener use depend on emissions from products, dynamic behavior of chemical species, and human factors. A series of experiments was conducted to investigate volatile organic compound emissions, concentrations, and reactive chemistry associated with the household use of cleaning products and air fresheners. Research focused on two common classes of ingredients in cleaning products and air fresheners: ethylene-based glycol ethers, which are classified as toxic air contaminants, and terpenes, which react rapidly with ozone. A shelf-survey of retail outlets led to the selection of 21 products whose chemical composition was characterized. Among the criteria used to select these products were ready availability through California retail outlets and, for the majority of products, expectation that they contained ethylene-based glycol ethers, terpenes and related compounds, or both. Of the 17 cleaning products characterized, four contained substantial levels of d-limonene (4-25% by mass), three contained terpenoids that are characteristic of pine oil, six contained substantial levels of ethylene-based glycol ethers (0.8-10% by mass), and five contained less than 0.2% of any of the target analytes. Xylene in one product was the only other toxic air contaminant detected. Among the four air fresheners characterized, three contained substantial quantities (9-14% by mass) of terpene hydrocarbon and terpene alcohol constituents, with linalool being the most abundant. Six of the 21 products were investigated in simulated-use experiments in which emissions and concentrations of primary constituents were measured. Cleaning products that contain 2- butoxyethanol as an active ingredient produced one-hour-average concentrations of 300 to 2,300 µg/m3 immediately after simulated typical use in a room-sized chamber. For cleaning products that contain d-limonene as an active ingredient, corresponding levels were 1,000 to 6,000 µg/m3. Application of a pine-oil based cleaner produced one-hour-average concentrations of 10-1300 µg/m3 for terpene hydrocarbons and terpene alcohols. Reactive chemistry was studied by exposing constituents of three products to ozone, both in a bench-scale chamber and during simulated use. Prominent products of the reaction of terpenes with ozone included formaldehyde (a toxic air contaminant), hydroxyl radical, and secondary organic aerosol (a form of fine particulate matter). Incorporating the new experimental data, exposures were estimated for several simulated use scenarios. Under ordinary circumstances, exposures to 2-butoxyethanol, formaldehyde, and secondary organic aerosol are not expected to be as high as guideline values solely as a result of cleaning product or air freshener use. However, ordinary use could lead to exposure levels of similar magnitude as guideline values. Scenario model results suggest that exposure levels could exceed guideline values under exceptional yet plausible conditions, such as cleaning a large surface area in a small room. The results of this study provide important information for understanding the inhalation exposures to certain air pollutants that can result from the use of common household products.
Main Report (PDF - 1,625K)
Appendix A -- Appendix D (PDF - 4,501K)
Appendix E (PDF - 1,959K)
Executive Summary
Background
Exposures to air pollutants cause health risks. The strategic plan of the California Air Resources Board (ARB) recognizes the importance of developing better knowledge of human exposure to air pollutants (http://www.arb.ca.gov/research/apr/apr.htm). The volatile organic compound (VOC) composition of consumer products sold in California is regulated by ARB to limit their contribution to photochemical smog production (http://www.arb.ca.gov/consprod/consprod.htm). However, use of cleaning products and air fresheners in indoor environments can also lead to the direct exposure of product users and other building occupants to air pollutants. Exposures of potential concern can occur because certain consumer products may be formulated with VOCs that are classified as toxic air contaminants (TACs). Of interest in this category are ethylene-based glycol ethers, which are classified as TACs, although with relatively low toxicities. These compounds are commonly used as solvents in cleaning products, causing many people to be routinely exposed as the products are used during household cleaning activities. Additional exposures of potential concern arise owing to reactive chemistry that occurs in the indoor environment. This chemistry converts nontoxic primary constituents into secondary pollutants that may pose human health risks. Of particular interest in this category are terpene-ozone reactions. Terpenes, a class of VOCs derived from plant oils, are widely used in cleaning products and air fresheners because of their favorable solvent properties and pleasant odors. Ozone generated in outdoor air enters indoor environments along with ventilation air. Ozone may also be emitted directly indoors from certain types of air cleaners and from photocopiers and printers. Some terpenes and related organic compounds react rapidly with ozone. Ozone-terpene chemistry produces the hydroxyl radical, which triggers an array of indoor chemical reactions, and formaldehyde, a TAC with a low acceptable exposure limit. This chemistry also converts some of the gaseous species into organic particulate matter, raising possible concerns because of the strong association between ambient particulate matter levels and a host of adverse health effects. The main objective of this research was to substantially increase our knowledge of the concentrations of air pollutants, especially TACs that occur in indoor environments owing to the use of widely available cleaning products and air fresheners, with and without the simultaneous presence of ozone.
Methods
The broad objective stated in the previous paragraph was achieved by the following means. First, we undertook a thorough review of published literature on air pollutant exposure associated with the use of cleaning products and air fresheners. Next, we conducted a shelf-survey of products that were available to consumers at five retail outlets in northern California. In a multistage process, 21 products were selected for further study considering these key criteria: (a) products are readily available to California consumers through retail outlets; (b) most products are either known or expected to contain substantial levels of reactive terpenes, terpene alcohols, other unsaturated compounds, or ethylene-based glycol ethers; and (c) the set of products includes at least one each of disinfectants, general-purpose degreasers, general-purpose cleaners, wood cleaners, furniture maintenance products, spot removers, multi-purpose solvents, and air fresheners. Then, we conducted measurements to characterize the VOC composition of the selected cleaning products and air fresheners. Using these results, six products were selected to study emissions and concentrations of the primary constituents during eighteen simulated-use experiments in a room-size research chamber. Three products were selected from the set of 21 to study secondary pollutant formation when combined with ozone. Fifteen experiments were carried out in a bench-scale chamber under well-controlled conditions. With the same products, eleven experiments were executed employing simulated use in the room-sized chamber, with and without the presence of ozone. These experiments examined the effect of ozone on the primary VOC constituents of the cleaning products and air freshener, as well as the resultant production of secondary pollutants, including formaldehyde, the hydroxyl radical, and fine particulate matter. Finally, analyses were carried out to interpret the new experimental results to better understand their significance for human inhalation exposure to air pollutants owing to the use of cleaning products and air fresheners indoors.
Results
Among the 21 products whose composition was tested, six contained ethylene-based glycol ethers, primarily 2-butoxyethanol, with levels ranging from 0.8% to 9.6%. Only one other toxic air contaminant, xylene, was detected, and in only one product. Twelve of the 21 products contained terpenes and other ozone-reactive compounds at overall levels ranging from 0.2% to 26%. Simulated full-strength use of cleaning products caused fractional emissions of terpenes and glycol ethers of 35-100% of the amount dispensed when towels were retained in the test chamber versus 20-50% when towels were removed. Floor mopping with a dilute solution of pine-oil based cleaner led to terpene emissions of 7-12% of the amount dispensed. Simulated cleaning product use caused peak 1-h average concentrations of the most prevalent target compounds to be in the range of a few hundred to a few thousand micrograms per cubic meter, as illustrated in Table ES-1.
When terpenes and related compounds in cleaning products and air fresheners were exposed to ozone, we consistently observed a high degree of reactive chemistry. The effects included reduced concentrations of primary constituents of the products, reduced ozone concentrations, enhanced concentrations of formaldehyde, measurable levels of the OH radical, and substantial secondary production of particulate matter. Table ES-2 illustrates this point by presenting data on ozone and volatile organic compounds from one experiment in which volatile constituents of a pine-oil-based cleaner were exposed to ozone.
Each of the fifteen experiments conducted in the bench-scale chamber produced a nucleation event in which substantial amounts of new ultrafine particles were generated as a consequence of the reactive chemistry. In the eleven room-scale simulated use experiments, we also observed substantial secondary pollutant formation, as illustrated in Table ES-3. The use of a terpene-containing cleaning product or air freshener in the presence of ozone (delivered through the ventilation supply air at 114-120 ppb) increased the formaldehyde levels by 6-12 ppb. The significance of regularly repeated exposures at such levels might be considered against California’s chronic reference exposure level for formaldehyde of 2 ppb. Likewise, the use of a terpene-containing cleaning product in the presence of ozone increased the fine particulate matter concentrations by approximately 30-90 micrograms per cubic meter. California’s standard for ambient fine particulate matter (PM2.5) is 12 micrograms per cubic meter on an annual average basis. California also has a 24-hour average standard of 50 micrograms per cubic meter for ambient levels of all particulate matter smaller than 10 micrometers in diameter.
Conclusions
The study results indicate that, in California and elsewhere, elevated inhalation exposures to air pollutants can be expected to occur under some circumstances owing to the use of common cleaning products and air fresheners. Several of the products studied contained and emitted substantial amounts of a single TAC, 2-butoxyethanol. This ethylene-based glycol ether was found to be an active ingredient in six of the 21 products characterized. The measured peak concentrations of 2-butoxyethanol owing to the use of these products were below relevant acute exposure guidelines. However, modeled exposures for high-use scenarios suggest that the California acute (one-hour) exposure level of 14 mg m-3 might be exceeded under some circumstances. Also of potential concern are the terpenes and related unsaturated organic compounds. These constituents are widely used as solvents and as scenting agents. Many species in this class react rapidly with ozone, leading to the formation of formaldehyde, a TAC with a low chronic reference exposure level, and particulate matter, a regulated pollutant class in ambient air. Other oxidation products are also formed with unknown toxicological properties (e.g., hydroperoxides from linalool.) Thus, it appears that, when compared with health-based concentration guidelines and standards, the levels of 2-butoxyethanol, formaldehyde and particulate matter associated with the use of certain consumer products can be high enough under some circumstances to warrant further consideration. Further consideration should also be given to the toxicological properties of yet-to-be-evaluated oxidation byproducts of ozone-terpene chemistry.
source: ftp://ftp.arb.ca.gov/carbis/research/apr/past/01-336_a.pdf 13jun2006
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