CRESOLS 147 6. POTENTIAL FOR HUMAN EXPOSURE 6.1 OVERVIEW o-Cresol, m-cresol, p-cresol, and mixed cresols have been identified in at least 210, 22, 310, and 70 of the 1,678 hazardous waste sites that have been proposed for inclusion on the EPA National Priorities List (NPL), respectively (HazDat 2006). However, the number of sites evaluated for cresols is not known. The frequency of these sites for o-, m-, p-, and mixed cresols can be seen in Figures 6-1, 6-2, 6-3, and 6-4, respectively. Cresols are widely occurring natural and anthropogenic products. Although cresols appear to be ubiquitous in the environment, their concentrations probably remain low due to their rapid removal rates in most environmental media. In air, cresols degrade rapidly because of reactions with photochemically produced hydroxyl radicals. Biodegradation is the dominant mechanism responsible for the fast breakdown of cresols in soil and water. Nevertheless, cresols may persist in extremely oligotrophic waters, in those with limited microbial communities, and/or those under anaerobic conditions, such as in some sediments and groundwater aquifers. Based on the available information, the most common route of exposure for the general population is inhalation. Cresols are constantly emitted to air via automobile exhaust; consequently, people who live in urban and suburban settings may be constantly exposed to low levels of cresols in the atmosphere. Cresols are also emitted to ambient air during the combustion of coal, wood, and municipal solid waste. Therefore, residents near coal- and petroleum-fueled electricity-generating facilities, municipal solid waste incinerators, and industries with conventional furnace operations or large-scale incinerators may be exposed to cresols in air. People in residential areas where homes are heated with coal, oil, or wood may also be exposed to cresols in air. High levels of cresol exposure can result from active and passive inhalation of cigarette smoke (Wynder and Hoffmann 1967). Therefore, people who smoke or live with smokers are exposed to higher concentrations of cresol in the air. 6.2 RELEASES TO THE ENVIRONMENT The Toxics Release Inventory (TRI) data should be used with caution because only certain types of facilities are required to report (EPA 2005). This is not an exhaustive list. Manufacturing and processing facilities are required to report information to the TRI only if they employ 10 or more full-time employees; if their facility is included in Standard Industrial Classification (SIC) Codes 10 (except 1011, CRESOLS 152 6. POTENTIAL FOR HUMAN EXPOSURE 1081, and 1094), 12 (except 1241), 20–39, 4911 (limited to facilities that combust coal and/or oil for the purpose of generating electricity for distribution in commerce), 4931 (limited to facilities that combust coal and/or oil for the purpose of generating electricity for distribution in commerce), 4939 (limited to facilities that combust coal and/or oil for the purpose of generating electricity for distribution in commerce), 4953 (limited to facilities regulated under RCRA Subtitle C, 42 U.S.C. section 6921 et seq.), 5169, 5171, and 7389 (limited S.C. section 6921 et seq.), 5169, 5171, and 7389 (limited to facilities primarily engaged in solvents recovery services on a contract or fee basis); and if their facility produces, imports, or processes ≥25,000 pounds of any TRI chemical or otherwise uses >10,000 pounds of a TRI chemical in a calendar year (EPA 2005). 6.2.1 Air Estimated releases of 3,313 pounds (~1.5 metric tons) of o-cresol, 41.496 pounds (~19 metric tons) of m-cresol, 31,393 pounds (~14 metric tons) of p-cresol, and 932,106 pounds (~423 metric tons) of mixed isomers of cresol, to the atmosphere from 23, 28, 27, and 157 domestic manufacturing and processing facilities in 2005, accounted for about <1, 21, 21 and 72% of the estimated total environmental releases of o-cresol, m-cresol, p-cresol, and cresol mixed isomer from facilities required to report to the TRI (TRI05 2007), respectively. These releases are summarized in Tables 6-1 through 6-4. A national emissions study conducted from 1990 to 1998 reported an estimated 11,000 tons/year released throughout the United States for all combined isomers of cresol (EPA 2000d). The emissions of total cresol isomers were 6,000 and 5,000 tons/year for urban and rural locations, respectively (EPA 2000d). Cresols are a group of widely distributed natural compounds formed as metabolites of microbial activity and excreted in the urine of mammals (Fiege and Bayer 1987). Cresols occur in various plant lipid constituents, including oils from jasmine, cassia, Easter lily, ylang ylang, and Yucca gloriosa flowers, peppermint, eucalyptus, and camphor. Oils from conifers, oaks, and sandalwood trees also contain cresols (Fiege and Bayer 1987). Volatilization of natural cresols from urine and transpiration of plants may release cresols to the air. Cresols are also a product of combustion and can be released to the atmosphere from natural fires associated with lightning, spontaneous combustion, and volcanic activity (McKnight et al. 1982). Cresols are natural components of crude oil and coal tar, from which they are recovered as fractional distillates. Cresols are also produced synthetically. The dominant anthropogenic sources for the release CRESOLS 153 6. POTENTIAL FOR HUMAN EXPOSURE Table 6-1. Releases to the Environment from Facilities that Produce, Process, or a Use o-Cresol b Reported amounts released in pounds per year Total release On- and c d e f g h i j k State RF Air Water UI Land Other On-site Off-site off-site AR 1 0 No data 0 0 0 0 0 0 IL 2 10 No data 0 5 250 10 255 265 KY 2 478 No data 0 0 0 478 0 478 LA 2 4 0 0 0 0 4 0 4 MO 1 10 No data 0 0 0 10 0 10 NY 3 1,000 5 0 0 0 1,005 0 1,005 OH 3 103 0 0 255 0 103 255 358 TX 7 1,695 118 182,006 10 1 182,358 1,472 183,830 WI 2 12 0 0 0 0 12 0 12 Total 23 3,313 123 182,006 270 251 183,981 1,982 185,963 a The TRI data should be used with caution since only certain types of facilities are required to report. This is not an exhaustive list. Data are rounded to nearest whole number. b Data in TRI are maximum amounts released by each facility. c Post office state abbreviations are used. d Number of reporting facilities. e The sum of fugitive and point source releases are included in releases to air by a given facility. f Surface water discharges, waste water treatment-(metals only), and publicly owned treatment works (POTWs) (metal and metal compounds). g Class I wells, Class II-V wells, and underground injection. h Resource Conservation and Recovery Act (RCRA) subtitle C landfills; other on-site landfills, land treatment, surface impoundments, other land disposal, other landfills. i Storage only, solidification/stabilization (metals only), other off-site management, transfers to waste broker for disposal, unknown j The sum of all releases of the chemical to air, land, water, and underground injection wells. k Total amount of chemical transferred off-site, including to POTWs. RF = reporting facilities; UI = underground injection Source: TRI05 2007 (Data are from 2005) CRESOLS 154 6. POTENTIAL FOR HUMAN EXPOSURE Table 6-2. Releases to the Environment from Facilities that Produce, Process, or a Use m-Cresol b Reported amounts released in pounds per year Total release On- and c d e f g h i j k State RF Air Water UI Land Other On-site Off-site off-site IL 2 10 No data 0 5 250 10 255 265 IN 6 28,159 No data 0 0 0 28,159 0 28,159 KS 1 3 No data 0 0 0 3 0 3 KY 1 785 No data 0 0 0 785 0 785 MI 1 3 No data 0 0 0 3 0 3 MO 2 270 0 0 0 0 270 0 270 MS 1 2,400 No data 0 0 0 2,400 0 2,400 NC 1 3 No data 0 0 0 3 0 3 NY 1 255 5 0 0 0 260 0 260 OH 1 1,144 0 0 500 0 1,144 500 1,644 OK 1 0 No data 0 0 0 0 0 0 SC 3 207 No data 0 0 0 207 0 207 TN 1 1,414 No data 0 0 0 1,414 0 1,414 TX 5 6,820 497 153,332 274 13 160,786 150 160,936 WV 1 23 42 0 1 0 65 1 66 Total 28 41,496 544 153,332 780 263 195,509 906 196,415 aThe TRI data should be used with caution since only certain types of facilities are required to report. This is not an exhaustive list. Data are rounded to nearest whole number. bData in TRI are maximum amounts released by each facility. cPost office state abbreviations are used. d Number of reporting facilities. e The sum of fugitive and point source releases are included in releases to air by a given facility. f Surface water discharges, waste water treatment-(metals only), and publicly owned treatment works (POTWs) (metal and metal compounds). g Class I wells, Class II-V wells, and underground injection. h Resource Conservation and Recovery Act (RCRA) subtitle C landfills; other on-site landfills, land treatment, surface impoundments, other land disposal, other landfills. i Storage only, solidification/stabilization (metals only), other off-site management, transfers to waste broker for disposal, unknown j The sum of all releases of the chemical to air, land, water, and underground injection wells.