Indoor Secondary Organic Aerosol Formation and Health Effects Annette C. Rohr, Sc.D. October 24, 2006 Health Effects of Organic Aerosols Workshop Palo Alto, CA Outline of Presentation Background Indoor air context, but important implications for ambient air Potentially important reactions Terpene/ozone reactions Secondary organic aerosol formation Health effects Research needs/knowledge gaps 2 1
The Indoor Environment: A Complex Mixture Mixture of gas- and particle-phase materials Infiltration of ambient air pollutants Indoor-specific sources (e.g., emissions from building materials, cooking, cleaning, etc.) Emerging field of indoor chemistry: reactions can occur between indoor pollutants to produce new materials 3 Indoor Chemistry: Possible Health Concerns Products may be more biologically active than their precursors Sick building syndrome symptoms? Lost TVOC linked to formaldehyde and symptom complaints (Sundell et al., 1993) Possible links to asthma/allergy? Formation of PM: reactions produce low vapor pressure compounds that can nucleate/condense 22% of limonene/ozone reaction products are aerosols Many reactions occur outdoors too 4 2
Potentially Important Reactions Ozone + unsaturated hydrocarbons Heterogeneous reactions [Ozone + nitrogen oxides (NOx)] [Thermal decomposition of peroxyacyl nitrates] [Free radical reactions] 5 Ozone + Unsaturated Hydrocarbons Reactions produce a variety of carbonyl products (C=O bond), e.g., aldehydes and carboxylic acids Polar VOCs Common products: formaldehyde, acrolein, methacrolein, methyl vinyl ketone, hydroxyl radicals (OH ) Common unsaturated hydrocarbons: terpenes Important reactions in ambient air 6 3
Common Indoor Sources of Unsaturated Hydrocarbons Indoor Source Unsaturated Hydrocarbon Wood flooring/furnishings Terpenes Linoleum, paints with linseed oil Linolenic, linoleic, and oleic acid Carpet 4-Phenyl/4-vinyl cyclohexene, styrene Odorants Limonene,!- and "-pinene Environmental tobacco smoke Styrene Certain waxes!-, "-Pinene, limonene, #-3-carene Cleaners, e.g. Pine-Sol Limonene,!-pinene,!-terpinene Animal fats Oleic acid, etc. Mold, fungi 1-Octene-3-ol Turpentine!-Pinene Photocopiers Styrene, limonene Humans Isoprene HVAC components Neoprene, styrene Weschler and Shields, Atmos Environ, 1999 7 Potentially Important Reactions Ozone + unsaturated hydrocarbons Heterogeneous reactions [Ozone + nitrogen oxides (NOx)] [Thermal decomposition of peroxyacyl nitrates] [Free radical reactions] 8 4
Heterogeneous Reactions Reactions on surfaces, e.g. floors, walls, HVAC components, particles Likely important, but understudied Surfaces of particular concern: Filters in HVAC systems: as filters load, surface area of collected particles becomes large. Materials in recirculated air partition onto the filters. Ozone in outside air can react with the sorbed chemicals, leading to desorption of products over an extended period of time. Carpets, latex paint: release formaldehyde upon reaction with ozone Formation of HNO 3 through reaction of NO 2 with surfaces 9 Terpene/Ozone Reactions Aldehydes, ketones, acids Carbonyl, carboxyl, hydroxyl groups Terpenes + Ozone Radicals (OH, Criegee, alkyl) Consumer products Cleaners Vegetation Electrical equipment Infiltration from outdoors Particle-phase materials Weschler and Shields (1999): office Long et al. (2000): residential Rohr et al. (2003): toxicological chamber Liu et al. (2004): full-scale chamber Hubbard et al. (2005): residential 10 5
Air Fresheners + Ozone Emitted terpenes With ozone: formaldehyde production With ozone: carbonyl production Liu et al., Environ Sci Technol, 2004 11 Organic Aerosol Formation in Terpene/Ozone Systems Numerous studies in laboratory, residential, and office settings 12 6
PM Formation in Homes: Ozone + Pine- Scented Cleaning Product Terpene Ozone No terpene, no ozone Hubbard et al., Indoor Air, 2005 13 Particle Size Distribution in!-pinene/ozone System Rohr et al., Aerosol Sci Technol, 2003 14 7
Health Effects of Terpene/Ozone Reaction Products Animal studies: terpene/ozone reaction products are airway irritants and may induce airflow limitation; cumulative effects are possible Only part of the response could be explained by known products, suggesting that unknown/unidentified irritants are formed New research at the Danish Institute of Occupational Health has identified new reaction products, e.g., secondary limonene endo-ozonide Controlled human exposures: eye irritation effects observed, no changes in BAL or lung function parameters 15 Sensory Irritation in BALB/c Mice Rohr et al., Inhal Toxicol, 2002 16 8
Airflow Limitation in BALB/c Mice Rohr et al., Inhal Toxicol, 2002 17 Isoprene/O 3 /NO 2 Reaction Products Wilkins et al., Environ Health Perspect, 2001 18 9
Effect of Repeated Exposures on Sensory Irritation 400 300 Exposure 1 Exposure 4 f (min -1 ) 200 100 0 0 30 60 90 120 150 180 210 Time (minutes) Rohr et al., Inhal Toxicol, 2003 19 Effect of Repeated Exposures on Airflow Limitation Rohr et al., Inhal Toxicol, 2003 20 10
Effect of Repeated Exposures on Airway Responsiveness Adapted from Rohr et al., Inhal Toxicol, 2003 21 Eye Blink Frequency BF change Lim/O 3 Iso/O 3 NO 3 O 3 Lim Iso/NO 2 Air Mean 42 18 21 0-12 -16-9 p-value <0.0001 0.056 0.022 0.98 0.13 0.053 0.26 Increase in BF indicates irritant response Largest response with limonene/ozone reaction products Points to importance of aerosol phase? Klenø and Wolkoff, Int Arch Occup Environ Health, 2004 22 11
Conclusions and Implications SOA formed indoors and in the ambient air through terpene/ozone reactions may have health effects Respiratory effects documented in mice Eye irritation documented in humans Aerosols from terpene/ozone reactions contribute to ambient SOA We need to better understand the potential health effects of these materials 23 Research Needs/Knowledge Gaps Other mixtures:! Other unsaturated hydrocarbons, e.g. linoleic acid, styrene, #-3-carene,!-terpinene! Other oxidants, e.g. NO 2 Continued investigation of terpene oxidation products! Mixture characterization! Exposure assessment! Contribution of particle phase products! Dose-response assessment! Other toxicological endpoints! Repeated exposures over a longer period of time at lower concentrations! Other animal models! Controlled human exposures 24 12