|IDENTIFICATION AND USE: m-Cresol is colorless, yellowish liquid. It is used as a bactericide for control of crown gall and olive knot on certain fruit and nut trees and ornamentals and the genetic/physiological disorder burr knot on apples. Currently, one product is registered which contains both m-cresol and xylenol. Used as disinfectant/bacteriocide/germicide for animal pathogenic bacteria (G- and G+ vegetative) in households, sickrooms, hospitals, veterinary clinics, and veterinary hospitals; on surgical instruments, diagnostic instruments/equipment and on hospital critical rubber/plastic items. Used as an insecticide and miticide on dogs for treatment of lice and fleas. It is also used for making synthetic resins; in photographic developers, explosives. Additionally, m-cresol is chemical intermediate for thymol used in cough/cold medicinals, synthetic pyrethroid insecticides, 3-methyl-6-t-butylphenol, trinitro-m-cresol for explosives, and phenolic resins; disinfectant ingredient; ore flotation agent; solvent. m-Cresol, either pure or mixed with p-cresol, is important in the production of contact herbicides. m-Cresol is also a precursor to the pyrethroid insecticides. Furthermore, many flavor and fragrance compounds, such as (-)-methanol and musk ambrette, are derived from m-cresol. Several important antioxidants including synthetic vitamin E are produced from m-cresol. Finally, m-cresol is used as a topical dental antiseptic, and it is also used in insulin preparations.
HUMAN EXPOSURE AND TOXICITY: o-Cresol, m-Cresol, and p-Cresol are metabolites of toluene and urinary levels are often used to monitor exposure to and metabolism of toluene. m-Cresol, o-Cresol, and p-Cresol are biomarkers for phenol exposure. The ability of m-Cresol to increase the permeability of human lung fibroblast membranes was reported. m-Cresol is used for endodontic treatments in dentistry and is cytotoxic to human dental pulp cells (D824 cells).
ANIMAL STUDIES: In an acute dermal toxicity study, technical grade m-cresol caused severe skin damage on at least 2/6 shaved, female, albino rabbits within 4 hours of application of 2830 mg/kg . m-Cresol, undiluted and in solution, can cause severe local irritation and corrosion following dermal and ocular exposure. Eye irritation can be severe and include corneal opacity. In other experiment, 215-464 mg/kg of m-cresol was given orally to rats in a single dose orally and resulted in hypoactivity, convulsions, GI tract inflammation, hyperemia, and death. 1,400-2,100 mg/kg of m-cresol was given to rabbits in a single dose orally and resulted in convulsions, coma, and death. 280-420 mg/kg of m-cresol was given to rabbits in a single dose iv and resulted in convulsions, coma and death. In a 28-day study, rats and mice of both sexes were given m-cresol at concentrations of from 300 to 30,000 ppm in the diet. All rats survived until study termination; some mice died at the 10,000 and 30,000 ppm dietary levels. Increased liver weights and kidney weights were noted in both species at doses as low as 3000 ppm. Bone marrow hyperplasia and atrophy of the uterus, ovary, and mammary gland were seen occasionally in both the 10,000- and 30,000-ppm groups. Groups of 10 rats of each sex were treated with m-cresol (0, 50, 150 or 450 mg/kg) in corn oil by gavage daily for 13 weeks. Convulsions were seen only in the groups treated with > 450 mg/kg. Hypoactivity, rapid labored respiration and excessive salivation were observed sporadically at doses of > 50 mg/kg. In spite of the observed clinical signs, few significant changes were found in rats performance on neurobehavioral test batteries, no brain weight changes were noted, and no gross or histopathological lesions in the brain or other nervous tissues were found. In developmental studies, m-Cresol caused maternal toxicity in rats and rabbits, but it caused no effects on the developing embryos at any dose. All three isomers of cresol are capable of promoting skin tumors initiated by a single dermal application of 9,10-dimethyl-1,2-benzanthracene (DMBA). m-Cresol did induce unscheduled DNA synthesis with metabolic activation, but not without. The results of SCE production, chromosome aberration, forward mutation, and dominant lethal mutation assays indicated no genotoxicity. m-Cresol was tested for ability to induce chromosomal aberrations in mouse bone marrow in vivo. No effect on chromosomal aberrations was found.
ECOTOXICITY STUDIES: The acute toxicity of the three disinfectants to young daphnids and embryos were hypochlorite > formaldehyde > m-cresol. The effects on growth mostly occurred in the late stages of organogenesis. Growth studies have shown that m-cresol is moderately toxic to aquatic bacteria, cyanobacteria (blue-green algae) and protozoa.