Why is exposure to environmental phenols relevant to health?
Environmental phenols (e.g., bisphenols, parabens, benzophenones and chlorophenols) are used in a variety of personal care products resulting in widespread human exposures. Some of them are metabolites of other environmental agents. Environmental phenols are a complex class of compounds. Bisphenol-A (BPA) and its newer analogs are found in plastics, thermal receipts, and many lotions and creams. Benzophenones are found in sunscreens and have been banned in certain areas because of damage to sea life. Another common environmental phenol is triclosan which is an anti-microbial agent found in soaps, toothpaste, and cleaning products.
Because of widespread use of products containing these compounds, exposure is prevalent. It can occur though ingestion, absorption through the skin, or inhalation. Women and children tend to be more highly exposed than men, given the types of products in which these chemicals are used.
Many environmental phenols are considered endocrine-disrupting chemicals and have been associated with a variety of hormone-mediated effects such as reproductive dysfunction, and in children reduced birth size, cognitive and/or behavior outcomes, asthma and obesity.
One phenol precursor - 1,4-dichlorobenzene - is an allergen and a probable carcinogen that is metabolized to 2,5-dichlorophenol.
What types of questions can be answered?
Some phenols are metabolites of other environmental agents and the phenols are excreted through the urine. Therefore, exposures are typically measured as urinary metabolites which reflect very recent (hours to days) exposures. Exposure over the last few days can be documented, and if repeated spot measurements are available, some insight can be gained about how constant exposures may be.
Many published data exist with which to compare these exposures, including general U.S. population urinary metabolite data published in CDC's National Report on Human Exposure to Environmental Chemicals.
How can exposure to environmental phenols be measured?
Exposure to a number environmental phenols can be documented using urinary biomarkers. Some phenols, such as nonylphenol, do not have good exposure biomarkers. Environmental samples such as house dust and silicone wristbands are also used to identify sources of environmental phenol exposures.
- Analytes: Free and bound forms of environmental phenols exist, as the parent phenols are metabolized or conjugated prior to excretion in urine. The free forms of some phenols may be biologically active, but their levels are sometimes quite low in biological matrices so may not be practically measured. Typically, the free and bound forms are measured together as total phenol metabolites. Although this total phenol measurement may not be reflective of the biologically active dose, it is a valid measure for total exposure.
- Methods: Various methods that couple liquid or gas chromatography with mass spectrometry are used.
- Types of biospecimens: Urine is the primary biospecimen used for these water-soluble metabolites. Phenols have been detected in other matrices including meconium, amniotic fluid, blood, breast milk, and follicular fluid, but non-urine matrices are not recommended due to typically low concentrations of biomarkers and potential for interference from external contamination at these low levels. Because concentrations of phenols vary with individual hydration, they are typically corrected for urine dilution when used in scientific research.
- Types of environmental samples: House dust and silicone wristbands are the most common media analyzed.
How does HHEAR ensure the quality of its analyses?
Contamination and use of improper storage vessels are significant concerns with these analytes, and proper inclusion of “field blanks” in a study helps identify any contamination. Knowing the types of collection equipment, processing materials, and storage vials, as well as potential sources of contamination—such as BPA-containing plastics—is important. Residue-grade water and reagents must be used during analysis.
Positive and negative controls are included in each analytic run. HHEAR labs participate in proficiency testing programs to monitor accuracy and reproducibility of analyses.
What sample quality and quantity are necessary?
Typically, 0.1-1.0 mL urine or one gram of dust is required, but more volume may be required if more than one class is to be measured. Too little quantity usually translates to lower frequency of detection. To test for some results, such as very high values, additional measurements are needed which also requires more sample. Appropriate containers must be used for collection of samples. Samples must not undergo repeated freeze-thaw cycles.
Centers for Disease Control and Prevention. National Biomonitoring Program Factsheet: Bisphenol A.
Liao C, Kannan K. A Survey of Alkylphenols, Bisphenols, and Triclosan in Personal Care Products from China and the United States. Archives of Environmental Contamination and Toxicology. 2014;67:50-59.
Liao C, Kannan K. Widespread Occurrence of Benzophenone-type UV Light Filters in Personal Care Products from China and the United States: An Assessment of Human Exposure. Environmental Science and Technology. 2014; 48:4103-4109.
Mustieles V, Pérez-Lobato R, Olea N, et al. Bisphenol A: human exposure and neurobehavior. Neurotoxicology. 2015;49:174-184.
Peretz J, Vrooman L, Ricke WA, et al. Bisphenol A and reproductive health: update of experimental and human evidence, 2007–2013. Environmental Health Perspectives. 2014;122(8):775-786.