Cresol sources

Synonyms 5-lsopropyl-2-methylphenol 5-lsopropyl-o-cresol Source Leeke, G. Gaspar, F. Santos, R. Ind. Eng. 

Until the late 1890s, coumarin was obtained commercially from only natural sources by extraction from tonka beans and deer tongue. Then synthetic methods of preparation and industrial manufacturing processes were discovered and developed starting principally from o-cresol, phenol, and sahcylaldehyde. Various methods can be used to obtain coumarin from each of these starting materials. 

Sources of Raw Materials. Coal tar results from the pyrolysis of coal (qv) and is obtained chiefly as a by-product in the manufacture of coke for the steel industry (see Coal, carbonization). Products recovered from the fractional distillation of coal tar have been the traditional organic raw material for the dye industry. Among the most important are ben2ene (qv), toluene (qv), xylene naphthalene (qv), anthracene, acenaphthene, pyrene, pyridine (qv), carba2ole, phenol (qv), and cresol (see also Alkylphenols Anthraquinone Xylenes and ethylbenzenes). 

Cresylic acid is a commercial mixture of phenolic compounds including phenol, cresols, and xylenols. This mixture varies widely according to its source. Properties of phenol, cresols, and xylenols are shown in Table 4-5 Cresylic acid constitutes part of the oxygen compounds found in crudes that are concentrated in the naphtha fraction obtained principally from naphthenic and asphaltic-based crudes. Phenolic compounds, which are weak acids, are extracted with relatively strong aqueous caustic solutions. 

When some values seem questionable a question mark in brackets is added next to these values. If two very different values are given for one substance the doubtful data source is noted. For instance, for o-cresol, two LD50 values for the rat orally are mentioned as follows LD50 o-r 121 1350 (Merck). This means that the 1350 value that seems high and that applies to a phenol that is particularly corrosive and toxic (see Code du travail (ie Labour Code)) was suggested by the Merck Index. 

Source U.S. EPA, Introduction to Hazardous Waste Identification (40 CFR, Part 261), Report U.S. EPA 530-K-05-012, U.S. EPA, Washington, DC, September 2005. a If o-, m-, and p-cresols cannot be individually measured, the regulatory level for total cresols is used. 

Fig. 9.72Structures of MCPA(4-chloro-2-methylphenoxyacetic acid (I)), its metabolites 4-chloro-o-cresol (II), 5-chloro-3-methyl catechol (III), 4-chloro-2-methyl muconic acid (IV), reagent pentafluorobenzyl bromide (V), and the derivatives VI-VIII from l-lll Source Reproduced with permission from the American Chemical Society [155]... 

A molecular sieve bed was used to purify continuously the fire-resistant hydraulic fluid (a triaryl phosphate) in a large hydraulic press. Periodically the sieve bed was regenerated by treatment with steam, and then purified air at 205°C. After 9 years of uneventful operation, the bed ignited on admission of hot air. The fuel source was traced to the accumulation of organic residues (phenols or cresols ) on the sieve which were not removed by the steam/air treatment. 

The crude oil used by Bennett and Barter (1997) was a typical North Sea oil generated from Upper Jurassic, Kimmeridge clay formation source rocks. The alkylphenol distribution in a sample of (Miller) crude oil, determined using solid phase extraction (SPE), is shown in Fig. 16.21. The crude oil is dominated by phenol and cresol and contains appreciable quantities of dimethylphenols. The concentrations of 2,3-, 3,4-, and 3,5-dimethylphenol also include a contribution from 2-, 3-, and 4-ethylphenols, because they coelute under the conditions employed (Bennett et ah, 1996). 

This Statement was prepared to give you information about cresols and to emphasize the human health effects that may result from exposure to it. The Environmental Protection Agency (EPA) has identified 1,177 sites on its National Priorities List (NPL). Cresols have been found at 25 of these sites. However, we do not know how many of the 1,177 NPL sites have been evaluated for cresols. As EPA evaluates more sites, the number of sites at which cresols are found may change. The information is important for you because cresols may cause harmful effects and because these sites are potential or actual sources of human exposure to cresols. 

Three types of closely related cresols exist ortho-cresol (o-cresol), meta- cresol (m-cresol), and para-cresol (p-cresol). Pure cresols are colorless chemicals, but they may be found in brown mixtures such as creosote and cresylic acids (e.g., wood preservatives). Because these three types of cresols are manufactured separately and as mixtures, they can be found both separately and together. Cresols can be either solid or liquid, depending on how pure they are pure cresols are solid, while mixtures tend to be liquid. Cresols have a medicinal smell (odor) and when dissolved in water, they give it a medicinal smell and taste. Cresols do not evaporate quickly from water, but in rivers and lakes, they can be removed quickly by bacteria. Dissolved cresols can pass through soil into underground water sources. This may be a problem at hazardous waste sites where cresols are buried. Once cresols are in the water table, they may stay there for months without changing. Cresols in air quickly change and break down into smaller chemicals, some of which irritate the eyes. Cresols can also irritate the eyes. 

Cresols are widely distributed natural compounds. As discussed above, they are formed as metabolites of microbial activity and are excreted in the urine of mammals (Fiege and Bayer 1987) and humans (Needham et al. 1984). Cresols from human urine are probably biodegraded at municipal sewage treatment facilities prior to release to ambient waters. However, for combined septic and storm sewage systems, cresols may be released to surface waters during periods of precipitation when influent volumes exceed treatment plant capacities. Also, in rural and suburban areas where septic tanks are used (o- and m-cresols can resist anaerobic digestion), human excrement may be a nonpoint source release of cresols to groundwater. 

Various plant lipid constituents contain cresols (Fiege and Bayer 1987). Runoff from terrestrial sources may contribute cresols to surface waters in addition to endogenous sources such as aquatic plants, animals, and microbes. 

In general, cresols will degrade in surface waters very rapidly. However, cresols may persist in groundwater due to a lack of microbes and/or anaerobic conditions. Cresols are largely released to groundwater via landfills and hazardous waste sites. Tables 5-2a through 5-2e include monitoring data for these sources. 

Monitoring data have not shown cresols to be widely occurring atmospheric pollutants. The National Ambient Volatile Organic Compounds (VOCs) Database, a compilation of published and unpublished air monitoring data from 1970 to 1987, contained very little information on the cresols (Shah and Heyerdahl 1989). The database contained only information for o-cresol in source-dominated atmospheres (air surrounding a facility or known release of the chemical in question). The median air concentration of o-cresol at source-dominated sites is 0.359 ppb for 32 samples (Shah and Heyerdahl 1989). 

Tables 5-2a through 5-2e summarize the literature data on cresols found in groundwater and their respective anthropogenic sources. STORET (1989) did not contain records for o-cresol in groundwater. 

Cresols have been identified as components of automobile exhaust (Hampton et al. 1982 Johnson et al. 1989 Seizinger and Dimitriades 1972), and may volatilize from gasoline and diesel fuels used to power motor vehicles. Vehicular traffic in urban and suburban settings provides a constant source of cresols to the atmosphere. Hence, urban and suburban populations may be constantly exposed to atmospheric cresols. Cresols are also emitted to ambient air during the combustion of coal (Junk and Ford 1980), wood (Hawthorne et al. 1988, 1989), municipal solid waste (James et al. 1984 Junk and Ford 1980), and cigarettes (Arrendale et al. 1982 Novotny et al. 1982). 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. 

The most common route of exposure for the general population is probably inhalation. However, cresols have a short residence time in both day- and night- time air despite continual releases of cresols to the atmosphere, levels are probably low. Very few atmospheric monitoring data are available in the literature therefore, an average daily intake via inhalation was not calculated. Cigarette smoke is also a source of atmospheric exposure. An individual who smokes two packs of cigarettes a day may inhale 3.0 pg/day (Wynder and Hoffman 1967). 

Hutchins et al. 1980 Oliveira and Sitar 1985 Ram et al. 1985 Sawhney and Kozlowski 1984 Stuermer et al. 1982 Weber and Matsumota 1987) only (sources of groundwater contamination include hazardous waste sites). Data describing the exposure levels in air and surface water are lacking. It is not clear whether monitoring studies were not performed, or were not found. Quantified levels of cresols in food are also lacking. Estimates of human intake are not available. 

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