Why is childhood environmental phenol exposure relevant to health?
Environmental phenols are used in a variety of personal care products resulting in widespread exposures in humans. Environmental phenols are a large and complex class of compounds, the most common being bisphenol A (BPA) and its newer analogs found in plastics, thermal receipts, and many lotions and creams and triclosan which is found in many anti-microbial products.
Because of widespread use of products containing these compounds, exposure is prevalent. It can occur though ingestion, absorption through the skin, or inhalation. Children and women tend to be more highly exposed than men.
Environmental phenols are considered endocrine-disrupting chemicals and have been associated with a variety of hormone-mediated effects such as reproductive dysfunction, reduced birth size, and childhood obesity.
Prenatal or childhood exposure has been associated with asthma and neurodevelopmental deficits in children. 1,4-Dichlorobenzene is an allergen and a probable carcinogen that is metabolized to 2,5-dichlorophenol. Environmental phenols have not been fully evaluated in children, and many studies are cross-sectional (i.e., all data were collected at the same time), which makes it difficult to identify cause-and-effect relationships.
What types of questions can be answered?
Many environmental phenols are rapidly metabolized into compounds with limited biological activity which 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 evaluated, and if repeated spot measurements are available, some insight can be gained about ongoing exposure.
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 most, but not all, environmental phenols can be measured using urinary biomarkers. Some phenols, such as nonylphenol, do not have good exposure biomarkers.
- Analytes: Free and bound forms of environmental phenols can be measured. The free forms of some phenols may be biologically active, but their levels are 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 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, they are typically corrected for urine dilution.
How does CHEAR 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. CHEAR 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 is required, but more volume may be required if more than one class is to be measured. Less volume usually translates to lower frequency of detection. Appropriate containers must be used for collection of samples. Samples must not undergo repeated freeze-thaw cycles.
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.