Dr. Brown is a public health scientist at the Southwest Pennsylvania Public Health Project, a nonprofit public health organization that assists and supports residents of Southwestern Pennsylvania and beyond who believe their health has been, or could be, impacted by unconventional oil and gas development (UOGD, or fracking). Dr. Brown is also the Public Health Toxicologist and Director of Public Health Toxicology for Environment and Human Health, Inc. He is the past Chief of Environmental Epidemiology and Occupational Health in Connecticut and was previously Associate Professor of Toxicology at Northeastern College of Pharmacy and Allied Health. He also served as Deputy Director of the Public Health Practice Group of Agency for Toxic Substances and Disease Registry (ATSDR) at the National Centers for Disease Control and Prevention in Atlanta, Georgia. Dr. Brown graduated from Cornell University in Biochemistry, received his MS from the University of California in Environmental Health, and his ScD from Harvard School of Public Health in Toxicology.
Volatile Organic Compounds (VOC) Impact on Cells and Organ Systems
VOC metabolites have been found in the urine of children and adults who live near shale gas facilities. VOCs make up 12% of the mixture in emissions. Multiple high exposures or continuous lower exposures exacerbate the biochemical and cellular effects. When complex mixtures are present synergistic effects are certain. Thus, the federal reference safety values are not sufficient to protect health.
The health effects from the VOCs are consistent with the principles that describe biochemical actions at the cellular and tissue level. Although, EPA defines VOCs as chemicals involved with photochemical formation of ozone, health effects are specific to the actual chemicals in the mixtures. Over 32 different VOCs are in the mixtures emitted. NOx, CO, PM 2.5 or PM 1 are also present.
Understanding the toxic effects of the chemicals is based on the cellular actions and the target organs affected. The physiological actions are specific to the class of VOCs present. There are 6 major classes: halogenated and non-halogenated alkanes, and alkenes, aldehydes, alcohols and Poly Aromatic Hydrocarbons (PAHs) eg. Benzene, toluene, xylenes and ethyl benzene. VOCs act on cell membranes, receptors that release bioactive moieties, or cellular energetics to inhibit function of organelles. The signs and symptoms reported are the result of this inhibition and the organ system(s) affected.
The current EPA test method TO15 is focused on chemicals with 5 carbons or more and does not necessarily quantitate chemicals 1 to 5 carbons in length. But short chain halogenated compounds such as chloromethane are present. Thus, the health actions present are dependent on the VOCs and other chemicals in the mixtures and the frequency and levels of exposure.
CME / CEU survey questions:
1. VOC emissions from shale sites are mixtures of volatile, low molecular weight chemicals. Two are aromatics compounds such as benzene, toluene, and xylene, and aliphatic compounds such as formaldehyde, hexane and propane. What are the target systems affected by these two groups of volatile chemicals?
2. The VOC mixtures are emitted with particles PM 2.5 and Nitrogen oxides. How do these compounds increase the exposure to the VOCS?
3. Irritation is an action of brief exposures to higher levels of certain VOCs present in shale gas emissions. What are two conditions associated with high susceptibility to VOC irritant exposures?