CAS No. 140-66-9
4-tert-Octyphenol, an alkylphenol, is used to manufacture alkylphenol ethoxylates, which are anionic surfactants used in detergents, industrial cleaners, and emulsifiers. Commercial formulations of alkylphenol ethoxylates usually contain a mixture of oligomers and isomers, and the polyethoxy chain may consist of up to 50 ethoxy units. Less frequently, the various alkylphenols have also been used as emulsifiers and modifiers in paints, pesticides, textiles, and some personal care products. Alkylphenols also have been used as plasticizers and antioxidants in plastics and resins. In the 1990s, over 500,000 tons of alkylphenol ethoxylates were produced annually worldwide. Nonylphenol ethoxylates are more commonly used than octylphenol ethoxylates. The alkylphenol ethoxylates enter the environment through human use of products containing them, through sewage, and through manufacturing waste streams (Warhurst, 1995; Ying et al., 2002). They are biodegraded to the corresponding alkylphenol (octylphenol or nonylphenol); to shorter chain alkylphenol ethoxylates; and to alkylphenoxycarboxylates. Octylphenols and nonylphenols can also enter the environment directly from manufacturing waste streams. During the 1980s and 1990s, several European nations banned the use of alkylphenol ethoxylates in domestic detergents and other uses. The alkylphenols can bioaccumulate in some fish, and some of their degradation products are toxic to aquatic life. In 1999-2000, 4-octylphenol monoethoxylate was detected in 43.5% of 139 U.S. streams in 30 states (Kolpin et al., 2002).
Human exposure to alkylphenols and alkylphenol ethoxylates may occur through ingestion of contaminated foods (e.g., fish) and drinking water, and from contact with some personal care products and detergents. Indoor and to a lesser extent, outdoor air may have detectable levels of 4-tert-octylphenol and 4-tert-octylphenol monoethoxylates, leading to inhalation as another potential exposure route (Rudel et al., 2003; Saito et al., 2004). In rats, orally administered 4-tert-octylphenol was well absorbed, did not bioaccumulate, and was quickly eliminated from the blood (Certa et al., 1996). Disposition in humans has not been studied sufficiently.
Human health effects from 4-tert-octylphenol or the corresponding octylphenol ethoxylates at low environmental doses or at biomonitored levels from low environmental exposures are unknown. Several alkylphenols, including 4-tert-octylphenol, have demonstrated estrogenic effects particularly when injected at high doses in animals. These high dose parenteral effects of 4-tert-octylphenol have included altered sex hormone levels and hypothalamic-pituitary suppression, impaired steroidogenesis, altered estrus cycles and reproductive outcomes, altered neonatal sexual development, testicular atrophy, and impaired spermatogenesis (e.g., Bian et al., 2006; Blake and Boockfor, 1997; Katsuda et al., 2000; Laws et al., 2000; Myllymaki et al., 2005; Nagao et al., 2001; Sweeney et al., 2000; Yoshida et al., 2001). It is unclear if estrogenic or other effects occur in animals through oral dosing, at lower or environmentally relevant doses (Blake et al., 2004; Tyl et al., 1999). 4-tert-Octylphenol is not considered directly genotoxic. IARC and NTP have not rated octylphenol, nonylphenol, or their corresponding ethoxylates with respect to human carcinogenicity.
Urinary levels of 4-tert-octyphenol reflect recent exposure. Urinary levels of 4-tert-octyphenol were detectable only at the 90th to 95th percentiles in the U.S. population, based on the representative subsamples of NHANES 2005-2010 (CDC, 2012). In a small number of adult Japanese volunteers, the urinary concentrations of 4-tert-octyphenol were near or below the detection limit (Inoue et al. 2003; Kawaguchi et al. 2004).
Finding measurable amounts of 4-tert-octylphenol in the urine does not imply that the levels of 4-tert-octylphenol cause an adverse health effect. Biomonitoring studies on levels of 4-tert-octylphenol provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of 4-tert-octylphenol than are found in the general population. Biomonitoring data can also help scientists plan and conduct research on exposure and health effects.
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