CAS No. 90-43-7
Ortho-phenylphenol (OPP, or 2-phenylphenol) and its water-soluble salt, sodium ortho-phenylphenate (SOPP), are antimicrobial agents used as bacteriostats, fungicides, and sanitizers. Both have been used in agriculture to control fungal and bacterial growth on stored crops, such as fruits and vegetables. SOPP is applied topically to the crop and then rinsed off, leaving the chemical residue, OPP. Most agricultural food applications have been revoked, but OPP and SOPP are still used on pears and citrus (U.S.EPA, 2006). OPP is still used as a disinfectant fungicide for industrial applications, on ornamental plants and turfs, in paints, and as a wood preservative. In the past, it was used in home sanitizers for surfaces. OPP is volatile and has limited water solubility, whereas SOPP is not volatile and is more water soluble. Both chemicals degrade within hours to weeks in the environment (U.S. EPA, 2006).
General population exposure can occur via dermal, inhalational, or oral routes from residential use and by ingesting treated food or food that was in contact with treated surfaces or equipment. OPP was detected in 40 of 60 different canned beers at concentrations in the low parts per billion (Coelhan et al., 2006). Estimated human intakes have been below recommended intake limits (U.S.EPA, 2006). Workers who manufacture, formulate, or apply these chemicals may be more highly exposed than the general population. OPP is efficiently absorbed from the gastrointestinal tract and through the skin, and is eliminated rapidly from the body as OPP glucuronide and sulfate conjugates (Bartels et al., 1998; Cnubben et al. 2002; Timchalk et al., 1998). Available evidence suggests that OPP does not accumulate in the body; however, small amounts of OPP have been measured in human adipose tissue (Onstot and Stanley, 1989).
Human health effects from OPP at low environmental doses or at biomonitored levels from low environmental exposures are unknown. OPP is considered to be moderately toxic after acute oral doses in animal studies. Chronic dosing in animals resulted in systemic effects such as weight loss and anemia, but no neurologic, reproductive, or developmental toxicity (Bomhard et al., 2002; U.S.EPA 2006). OPP was not mutagenic. Dermally-applied OPP was not carcinogenic in a 2-year experimental in animals (NTP, 1986). In high dose animal studies, OPP or SOPP produced carcinomas of the bladder only after phase II detoxification pathways were saturated, leading to production of two metabolites, ortho-phenylhydroquinone or ortho-phenylbenzoquinone. These metabolites may induce carcinogenicity via nongenotoxic regenerative hyperplasia of the bladder (Appel, 2000; Bomhard et al., 2002; Brusick, 2005; Kwok et al., 1999; Nakagawa et al., 1992; Smith et al., 1998; U.S.EPA 2006), or, less likely, by possible genotoxic mechanisms (Hagiwara et al., 1984; Ito et al., 1984; Murata et al., 1999; Pathak and Roy, 1993; Zhao et al., 2002). IARC has classified SOPP as a possible human carcinogen and OPP as not classifiable as a human carcinogen. Additional information is available from U.S.EPA at: https://www.epa.gov/pesticides/.
Urinary OPP levels reflect recent exposure. Detectable levels were seen in less than half the U.S. population in the subsamples from NHANES 2005-2006, 2007-2008, and 2009-2010 (CDC, 2012). Volunteers exposed to 0.4 mg dermally had urinary levels of OPP that were several hundred times higher than median levels found in NHANES 2003-2004 (Bartels et al., 1997; CDC, 2012).
Finding a measurable amount of OPP in urine does not imply that the level of OPP causes an adverse health effect. Biomonitoring studies on levels of OPP provide physicians and public health officials with reference values so that they can determine whether people have been exposed to higher levels of OPP 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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