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Health Risk Assessment



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AMI is the leading authority in health risk assessment (HRA) studies of air toxics and other hazardous materials. We have developed several models that are recognized as state-of-the-science in the Assessment of Chemical Exposure (ACE). A well-known model in the ACE family is  the ACE2588 model developed by AMI for the California Air Toxics Hotspots (AB 2588) program. The ACE2588 model has been accepted and recommended by regulatory agencies and used by AMI and others in HRAs for hundreds of facilities throughout California, other parts of the U.S. and even in foreign countries. Recently, AMI has developed the ACEHWCF model based on U.S. EPA-guidelines for hazardous waste combustion facilities. AMI has also developed MCACE (Monte Carlo Assessment of Chemical Exposure) that incorporates the Monte Carlo uncertainty analysis technique to provide more realistic risk estimates. The ACEME model has recently been developed for Monte Carlo probabilistic risk assessment for mercury emissions from coal-fired power plants and waste incinerators.  AMI is also familiar with the HARP (HotSpot Analysis and Reporting Program) model recently released by the California Air Resources Board and OEHHA. Representative projects performed by AMI include the following:

Development of a Comprehensive Risk Assessment Model for Hazardous Waste Combustion Facilities

AMI has recently completed the development of the health risk assessment model ACEHWCF (Assessment of Chemical Exposure for Hazardous Waste Combustion Facilities). The ACEHWCF model fully implements the recent guidelines from the U.S. EPA ( Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities). Similar to the AMI-developed and widely used ACE2588 model, ACEHWCF is a multi-source, multi-pathway, multi-pollutant and multi-receptor model that allows a comprehensive and accurate assessment of potential health risks (both carcinogenic and non-carcinogenic) from either a single facility or several facilities in a cumulative/regional analysis.

The ACEHWCF model can interface with regulatory dispersion models, such as ISCST3, ISC3-PRIME, AERMOD and CALPUFF. An efficient algorithm has been implemented to handle several pollutants, receptors and sources without incurring large amount of disk storage space. In addition to inhalation risks, the multipathway exposure algorithms recommended by the U.S. EPA are used to evaluate indirect (or non-inhalation) risks from dermal absorption, ingestion of soil, drinking water and food. Food ingestion includes consumption of vegetables, beef, pork, milk, eggs, poultry, fish and mother's milk. To accommodate a wide variety of local settings, the ACEHWCF model can evaluate risks from food sources located either onsite (homegrown) or offsite.

For each receptor location, the ACEHWCF model computes potential risks for EPA-recommended exposure scenarios (adult resident, child resident, subsistence fisher, subsistence fisher child, subsistence farmer and subsistence farmer child). Noncancer health effects (both acute and chronic) are quantified through hazard quotients or indices. Hazard quotients can be computed for affected target organs. Predicted cancer risks and noncancer hazard indices are tabulated both by pollutants and by emission sources. An user-friendly, menu-driven preprocessor PreACEHW is also available to assist the model user in setting the input file with a minimal amount of time and effort.

ACEHWCF incorporates many capabilities of the AMI-developed ACE2588 model that has widely been used, since 1991, in health risk assessment for hundreds of facilities in California and elsewhere. Usage of the ACEHWCF model should significantly save time and cost in preparing the risk assessments and expedite their review and approval by regulatory agencies.

Development of a Comprehensive Risk Assessment Model for AB 2588 Applications

In 1990, AMI developed the comprehensive risk assessment model ACE2588 (Assessment of Chemical Exposure for AB 2588) under a contract to the Santa Barbara County Air Pollution Control District. The model is specifically designed for detailed risk assessments, especially those required by the Air Toxics "Hot Spots" Information and Assessment Act (AB 2588). The model incorporates the algorithms and recommendations of the CAPCOA Risk Assessment Guidelines. The ACE2588 model is capable of evaluating potential health effects (both carcinogenic and non-carcinogenic) of several toxic substances emitted by multiple sources.

For calculating ambient air concentrations, the ACE2588 model can interface with several guideline dispersion models recommended by regulatory agencies such as ISCST3 and COMPLEX I. For multipathway pollutants, the model computes non-inhalation doses and risks through dermal absorption, ingestion of water, soil and food. Food ingestion includes consumption of vegetables, meat, dairy products, fish and mother's milk.

Carcinogenic effects are quantified by the individual lifetime cancer risk at each receptor location and the population excess cancer burden. For non-cancer pollutants, hazard indices are computed by the model to quantify health effects due to acute and chronic exposures. For acute and chronic exposure, the ACE2588 model computes hazard indices for all affected toxicological endpoints including cardiovascular system, central nervous system, immune system, kidney, liver, reproductive system and respiratory system.

The ACE2588 model is approved by regulatory agencies for use in AB 2588 health risk assessment. It has been applied by AMI and others to over 1000 facilities located throughout California and elsewhere, including those in foreign countries. The ACE2588 latest version has incorporated the most recent (Oct 2000) guidelines from California Air Resources Board and OEHHA. The ACE2588 model has also been included in the ATIRAS (Air Toxics Inventory Report and Analysis System) package that performs all tasks necessary in a facility risk assessment: emissions inventory, risk prioritization, dispersion modeling, risk assessment and computer graphics. 


Health Risk Assessment for Los Angeles Generating Stations  

AMI is currently involved in performing dispersion modeling and health risk assessments for power plants operated by Los Angeles Department of Water and Power (LADWP) in Los Angeles County. The  model ISCST3 is used for dispersion modeling for both criteria pollutants and air toxics, and the model HARP (HotSpot Analysis and Reporting Program) for multipathway health risk assessment. These modeling efforts are part of the permit applications for these facilities.


AB 2588 Facility Ranking and HRA Review in the South Coast Air Basin

For the South Coast Air Quality Management District, AMI performed a ranking study of approximately 1400 facilities which emit air toxics in the South Coast Air Basin. AMI modified the CAPCOA ranking procedure to accommodate facility operational hours, distances to nearest residence and business and multipathway pollutants. For efficient analyses, AMI developed a computer program for the ranking procedure. Results of the facility scoring and ranking were used by SCAQMD to prioritize each facility. Facilities in Category A (High Priority) are required to perform health risk assessment. Under another contract, AMI was in charge of reviewing the health risk assessments submitted by these facilities and also performed revisions and/or re-modeling for HRAs that were found to be deficient.

AB2588 Health Risk Assessment for Oil Refineries in Kern County

AMI performed comprehensive AB 2588 health risk assessments for air toxics emitted from refineries operated by Kern Oil, San Joaquin Refining and Gibson Oil in Kern County. These HRAs include dispersion modeling of the estimated air toxic emissions followed by a multi-media assessment of potential health impacts on the surrounding population. The ISCST model was used for dispersion modeling and potential health risks were predicted by the AMI-developed ACE2588 risk assessment model.

AB 2588 Health Risk Assessment For ARCO Oil & Gas Facilities

AMI completed comprehensive health risk assessments for air toxics emitted from several ARCO facilities located in Santa Barbara and Ventura Counties. These oil and gas production, processing, distribution facilities include numerous points of release and all types of air toxics. Based upon the guidelines of Santa Barbara and Ventura Counties, the ISCST dispersion model and the AMI-developed ACE2588 model were used in the risk assessments.

AB 2588 Health Risk Assessment for Mineral Facilities

AMI conducted AB 2588 health risk assessments for mineral facilities operated by NRM Corporation in Monterey County. Both the flat terrain model ISCST and the complex terrain COMPLEX I were used for dispersion modeling. The AMI-developed ACE2588 model was applied to perform a multi-pollutant, multi-pathway risk assessment.

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