Air Quality

Quantification of chemical concentrations in air and evaluation of inhalation exposures have evolved over the years, with advances in monitoring and modeling approaches. We can now measure many chemicals in air at concentrations below levels associated with potential adverse effects, an ability that raises important questions about sources and migration pathways. ToxStrategies consulting scientists have been active in these endeavors on behalf of our clients, and use the best science to understand critical factors such as ambient background concentrations, migration pathways, and collocated sources. Further, we are experienced with data management and analysis when working with extensive air monitoring data sets.

ToxStrategies consulting scientists provide a wide variety of services related to chemicals in air and potential human exposures and health effects, including:

  • Human health risk assessment for air toxics
  • Vapor intrusion evaluations
  • Air quality and community health
  • Critical review of air monitoring data
  • Evaluation of background air concentrations
  • Integration of air dispersion modeling
  • Public outreach and risk communication
  • Litigation support
  • Toxicological evaluations

Some key projects in these areas include:

  • Analyzed the effect of wind direction on air monitoring data for particulate matter (PM10 and PM5) to identify potential sources of PM in an area (masking analysis). This analysis identified traffic as the largest contributor to PM concentrations in the area and demonstrated that industrial sources were, in fact, a relatively small contributor.
  • Evaluated biomonitoring data collected in individuals living in an area near petroleum refineries, to address allegations that high levels of benzene in blood were due to facility operations. This project involved incorporating information on the pharmacokinetics of benzene and assessing the correlations between benzene concentrations in blood and ambient air, in studies in the published scientific
  • Developed a GIS-based model that incorporated air monitoring data for benzene collected over a period of 15 years at 18 monitoring locations in an urban area that hosts a number of industrial sources, including petroleum refineries. Used the model to calculate long- and short-term exposures to benzene; to evaluate the potential for adverse health effects associated with monitored concentrations of benzene, the long-term trends in benzene concentrations, and the impact of an operational upset at an industrial facility; and to conduct an assessment of short-term odor concerns. Presented findings of these analyses to community leaders and interested parties, including the City Council, County Commissioners, local newspaper editorial staff, school boards, and other stakeholders.
  • Evaluated toxicology literature and data regarding the potential for air contaminants associated with paper-mill operations to cause adverse health effects in the surrounding community. Also determined whether available toxicology data indicated that the current USEPA National Ambient Air Quality Standards (NAAQS) for NO2, SO2, and PM10 are protective of adverse respiratory effects in
  • Assessed the potential impacts of natural gas exploration and production operations on air quality in communities surrounding these operations. This project involved comprehensive assessments of available air monitoring, emissions inventory, and biomonitoring data and included developing fingerprints of potential contaminants associated with these types of operations, as well as evaluating measured and estimated air concentrations relative to health benchmarks and background air Results were published in the peer-reviewed literature (Bunch AG, Perry CS, Abraham L, Wikoff DS,Tachovsky JA, Hixon JG, Urban JD, Harris MA, Haws LC. 2014. Evaluation of impact of shale gas operations in the Barnett Shale region on volatile organic compounds in air and potential human health risks. Sci Tot Environ 468-469:832-842.
  • Researched mechanisms of action underlying benzene toxicity in order to assess potential health risks associated with intermittent exposures in
  • Collected ambient air monitoring data to identify air emission sources in the vicinity of a facility with metal-grinding operations. Evaluated emissions from metal-grinding operations to complete California’s AB2588 process, including critical analysis of the Air Toxics Inventory Report (ATIR), preparing a Health Risk Assessment (HRA), participating in a community meeting, and evaluating effectiveness of risk reduction measures.
  • Worked with a heat-treating facility and the regulatory agency to develop a compliance approach based on ambient monitoring that would allow the facility to continue operations after elevated concentrations of a site-related metal were measured in the vicinity. Evaluated emissions from heat-treating operations in compliance with California’s AB2588 process, including preparation of ATIR, HRA, and a Risk Reduction Plan. Air monitoring conducted by SCAQMD was assessed and used to address inaccuracies in the restrictive agency HRA assumptions and to demonstrate the limited extent of impact above urban background.
  • In support of litigation, evaluated residential exposures via vapor intrusion of trichloroethylene (TCE) and related chlorinated solvents identified in a groundwater plume flowing from an industrial area into a nearby residential neighborhood. Identified potentially affected properties; engaged in community outreach, including door-to-door consultation; performed residential indoor and ambient air sampling to assess the potential for vapor intrusion; and communicated the results and implications to residents. Worked with regulatory agencies as representative toxicology experts on the project, and successfully reduced the scope of investigation from the entire neighborhood to a limited number of homes.
  • Comprehensively analyzed the impacts to an urban area from oil and gas refinery operations. Evaluated 243 chemicals using more than 5.5 million data points. Assessed the potential for acute and chronic health effects by comparing measured air concentrations to federal and state health-based air comparison values. Conducted multiple linear regression analyses to identify upward and downward trends associated with air toxics in the region. Investigated meteorological trends that influence the migration of air pollutants from refinery operations.
  • In support of litigation, evaluated subsurface soil, soil vapor, and groundwater data to assess potential vapor intrusion to a proposed senior living facility. Evaluated most likely potential exposures to workers and residents based on a building configuration that included underground parking. Included research on ambient concentrations of benzene, particularly in parking structures.