Why is childhood exposure to VOCs relevant to health?
Volatile organic compounds (VOCs) are common products of incomplete combustion, occurring widely in air pollution, vehicle exhaust, and tobacco smoke. VOCs are also common constituents of cleaning and degreasing agents, deodorizers, dry-cleaning processes, paints, pesticides, and solvents. Increased concentrations of VOCs in the body can, therefore, result from a variety of environmental exposures.
Prior studies indicate that exposure to toxic VOCs such as benzene, butadiene, and toluene during early childhood increases the risk of leukemia and retinoblastoma.
What types of questions can be answered?
Exposure to VOCs can be measured by determining levels of their metabolites in urine or certain parent substances in blood. Most humans have these substances in their blood or urine, as some of them are the results of endogenous metabolic processes.
How can VOC exposure be measured?
- Analytes: Many VOCs such as acrolein, propylene oxide, and benzene are metabolized by the glutathione S-transferase pathway leading to the excretion of mercapturic acids in urine; these metabolites can be quantified. The mercapturic acid measurements in urine are particularly useful because the levels of these substances are generally well within the quantifiable range using current methods. Virtually all urine samples will contain these metabolites, but levels in exposed subjects may be significantly higher. Some VOCs (parent compounds) can also be quantified in serum and whole blood.
- Methods: Methods that couple chromatography with mass spectrometry are used.
- Types of biospecimens: Urine and serum. Because urine concentrations vary, analytes measured in urine need to be corrected for urine dilution.
How does CHEAR ensure the quality of its analyses?
All assays are well validated with respect to accuracy and precision. All assays have embedded positive and negative controls. The positive controls are used to check assay accuracy within each set of samples. The negative controls are generally water blanks that are included to assess the possibility of any cross contamination in the assay procedure.
What sample quality and quantity are necessary?
This is highly dependent on the assay to be run, but in general a few milliliters of urine or 0.5 mL of serum are required.
Filippini T, Heck JE, Malagoli C, et al. A review and meta-analysis of outdoor air pollution and risk of childhood leukemia. Journal of Environmental Science and Health. Part C. Environmental Carcinogenesis and Ecotoxicology Reviews. 2015;33(1):36-66.
Hecht SS, Yuan JY, Hatsukami D. Applying tobacco carcinogen and toxicant biomarkers in product regulation and cancer prevention. Chemical Research in Toxicology. 2010;23(6):1001-1008.
Heck JE, Park AS, Qiu J, et al. Risk of leukemia in relation to exposure to ambient air toxics in pregnancy and early childhood. International Journal of Hygiene and Environmental Health. 2014;217(6):662-668.