Quantification of chemical concentrations in air and exposures from deposited contaminants have evolved in recent years, with new advances in monitoring and modeling. We can now measure many chemicals in air at concentrations below levels associated with potential adverse effects, collect long-term air samples, and evaluate citizen science and community monitoring efforts. We also have publicly available data for air toxics (both measured and modeled) that can be used to inform our analyses. ToxStrategies uses the deep knowledge of available resources and innovative methods to understand and assess ambient background concentrations, migration pathways, and comingled sources to develop estimates of exposure and potential human health risk. Further, we are experienced with data management and analysis when working with extensive air monitoring data sets. ToxStrategies provides a wide variety of services related to air toxics and pollution.
Emission Source Characterization
- Use site-specific data to characterize industrial and commercial emissions
- Use publicly available data and literature to characterize emission sources and source allocations
Air Dispersion Modeling
- Perform air dispersion modeling of vapors and particulate matter, including deposition
- Use data visualization tools to analyze model results and identify maximally exposed individuals or sensitive subpopulations
Vapor Intrusion
- Use site-specific subsurface, indoor air, and ambient air data to characterize vapor intrusion
- Calculate site-specific attenuation factors and model vapor intrusion exposures
Air Sampling and Analysis
- Develop air sampling & analysis plans
- Evaluate quality and implications of monitoring data
- Perform statistical analyses of data, including spatial and temporal analyses
Litigation Support
- Expert witness and expert consulting support
Human Health Risk Assessment
- Integrate exposure science, toxicology, and epidemiology to characterize human health risks to air contaminants
- Develop conceptual exposure models of chemical releases to air, fate & transport, and exposures to relevant populations
- Evaluate potential exposure to deposited air emissions, including bioaccessibility/bioavailability
Screening and Monitoring Levels
- Develop site-specific concentration objectives for industrial or remedial activities
Regulatory Support
- RCRA TSDF
- TSCA
- Proposition 65
- State Regulatory Frameworks (e.g., California’s Air Toxics Hot Spots Rule 1402, Cleaner Air Oregon)
- Local regulatory requirements (e.g., South Coast Air Quality Management District’s Proposed Rule 1435)
Public Outreach and Risk Communication
- Develop community outreach presentations
- Present results in community meetings
Case Study #1: Air Toxics Human Health and Ecological Risk Assessment in Support of a RCRA Facility Permit
To support our client’s application for a RCRA permit to operate, ToxStrategies developed process emission estimates, an air dispersion model, and a human health and ecological risk assessment for an open burning/open detonation hazardous waste treatment facility in Northern California. The multi-chemical, multi-pathway risk assessment addressed deposition of particulates following detonation, potential exposures to water in an on-site fire water pond and nearby reservoir, and potential exposures to the nearest residents and cattle grazing in the open space surrounding the facility. The risk assessment was approved by the California Department of Toxic Substances Control (DTSC) and lead to a final RCRA permit to operate for the facility.
Case Study #2: Vapor Intrusion at a Former Dry Cleaners
Emblematic of many of our vapor intrusion projects, ToxStrategies was asked to evaluate soil gas data collected at a former dry cleaning operation in the Central Valley of California. Our process includes reviewing initial data, developing a conceptual site model, advocating for additional data only as necessary (e.g., seasonal, indoor air, ambient air, etc.), conducting a screening evaluation using default regulatory values, and developing a multiple lines of evidence approach for site-specific attenuation factors. In this and many cases, we successfully advocated for no further action with the regulatory agency because vapor intrusion was not demonstrated to be a public health risk based on site-specific conditions.
Case Study #3: Toxic Substances Control Act (TSCA)
To support the TSCA chemical prioritization process, ToxStrategies was asked to characterize general population exposure to acrylonitrile via ambient air and to assess the suitability of EPA monitoring and modeled data for use in regulatory risk assessment. We evaluated EPA’s air monitoring data from its Air Quality System (AQS) from the past 11 years and modeled data from EPA’s 2020 AirToxScreen assessment. Overall, findings from this study suggest that general population exposure to acrylonitrile from the ambient air is low and AQS data is well suited for general population exposure evaluations. These results benefit the general public in understanding their potential exposure to acrylonitrile, the EPA by informing their TSCA risk evaluation for acrylonitrile, and other researchers aiming to utilize AQS data for general population exposure assessments.
Click link below for ToxStrategies’ Air Quality Publications