Cambridege Environmental

58 Charles Street
Cambridge, MA 02141
Phone: 617-225-0810

411 Aviation Way
Frederick, MD 21701
Phone: 301-695-0251

Health & Ecological Risk Assessment

Risk assessment is the quantitative or qualitative evaluation of the potential for physical harm to result from a release of chemicals or pathogens. Risk assessment considers information describing an actual or potential release of chemicals or pathogens, the opportunity for human contact with the chemicals or pathogens, the potential level of exposure, the health effects of these agents, and the expected degree of harm. Risk assessments can be performed for hazardous waste sites, exposure to chemicals in the workplace or in consumer products, for waste incinerators, and many other situations. Many federal and state regulatory programs use or require risk assessments.

Cambridge Environmental specializes in quantitative assessment of risks to health and the environment posed by chemical, physical, and microbiological agents. We apply regulatory risk assessment techniques, but also implement more rigorous methods when the regulatory approaches are inappropriate or inadequate. We construct models based on first principles of science and engineering, support them by experimental data, and address uncertainties. Our assessments are guided by local concerns, guidelines, policies, and precedents.

Risk assessment confronts uncertainties at every step. When needed, we use probabilistic methods such as Monte Carlo simulations to quantify these uncertainties and to characterize risk more completely. Members of our staff are nationally recognized experts in the areas of uncertainty and probabilistic analyses of environmental and health risks.

We conduct multi-pathway human health risk assessments for new facilities (e.g., electric power plants, incinerators, manufacturing plants), existing facilities (e.g., power plants, refineries, waste-treatment plants), and the sites of retired facilities (e.g., smelters, manufactured gas plants, landfills/waste disposal sites). Substances that have been the foci of these assessments include arsenic, lead, mercury, vanadium, chlorinated alkenes, dioxins/furans, PCBs, pesticides, and radioisotopes. In every case, our risk assessments are site-specific and take into account the latest scientific and regulatory developments for the chemicals of concern.

Some of our projects have focused on ecological issues as well as on impacts to human health. Careful assessments of effects on community structure and ecosystem dynamics require efficient and sophisticated tools. Among the tools employed, we have found that use of RISK-ON-SITE - software developed by Cambridge Environmental - can provide valuable information on environmental and ecological impacts. For example, RISK-ON-SITE allows the overlay of habitat areas on a map of chemical concentrations on a site; thus we may estimate contaminant concentrations that are specific to individual habitats. This approach is superior to the use of simple site-wide averages or hot spot estimates.


City's Health Risk Concerns

In one recent project, we addressed health risk concerns for the City of Akron, Ohio. The local press had printed articles describing emissions from the city's municipal solid waste-to-energy facility as a "toxic witches' brew." Cambridge Environmental was called upon to assess immediate and long-term risks to health. We held a series of meetings with the Mayor's office, the press, and other concerned citizens; gathered relevant data on the facility and its environs; and developed a protocol for an holistic but efficient quantitative assessment. We presented and negotiated this protocol with the Ohio EPA and the Akron City Department of Health. The results of our analyses demonstrated that risks to health of residents most affected by stack emissions were negligible. We delivered a fully documented report to the Ohio EPA; the report was peer-reviewed and approved. Cambridge Environmental conveyed the results in a series of meetings and press conferences. Dissent was defused, and our client - the city - received high praise from the media and regulatory agencies for its expeditious and prudent handling of the matter.

Assesment of Former Industrial Facility

The Massachusetts Environmental Protection Act, and subsequently the Massachusetts Contingency Plan, required a risk assessment for this 90-acre site in Beverly, MA. Since 1902, the site contained the plant of the United Shoe Machinery Corp. Activities at the site were principally related to metal-working, together with support and utility services, including a coal-fired power plant that was subsequently changed to oil firing. Throughout the site's long history, various spills of oils, metals, coal ash, and other potentially hazardous materials occurred at well-defined locations, in addition to the random contamination that is likely to occur on any industrial facility. The risk assessment was required in order to evaluate whether clean-up was required, and if so to what extent, if the site were to be developed for various different uses in different areas.

A thorough investigation of the site resulted in 454 samples, each analyzed for 60 chemical or physical parameters. Since different areas of the site might be used for different purposes, a risk assessment method that could distinguish between different areas of the site, including indoor and outdoor areas, was required. A comprehensive methodology, based on the use of Voronoi diagrams, was developed and implemented as a mathematical and graphical computer program. Each measurement was extrapolated to adjacent parts of the site, so that every point on the site was assumed to be contaminated at the level found in the nearest measurement point. This was done independently for all contaminants at the site. Each area was then treated as a source for each contaminant, and time-dependent source models were developed for emissions and air dispersion from that source, taking account of all available characteristics of the source area.

The effects of the site were evaluated at a grid of 544 receptor points spread over the site, in order to distinguish the spatial variation across the site. The exposures from each source and each contaminant were summed at each receptor point, and the potential effect of such exposures evaluated by comparison with standards or guidelines either obtained directly from regulatory bodies or developed specifically for the purpose from the literature. A slightly simplified version of the complete procedure was then applied iteratively to estimate required clean-up levels, by evaluating at each iteration the worst-case contributing chemical and reducing the value of the clean-up level until every receptor point met an overall risk standard.

Potential PCB Leaks

Reports of PCB contamination of domestic water wells after failure of their submersible pumps led to a concern with the potential health effects of leaks of a non-PCB containing coolant oil in a similar line of domestic submersible water pumps. This project was designed to estimate the magnitude of potential leaks of oil from such pumps, and the magnitude of any health effects that might result.

The magnitude of potential leaks of oil from pumps was evaluated by examining historical information and by a technical, engineering analysis of the pumps themselves. Leak rates in normal operation were calculated by the application of physical principles to the design of the seals in the pumps, coupled with bounding estimates from the approximately known lifetime of the pumps. Leak rates in catastrophic circumstances were estimated using bounding estimates based on the total amount of oil present. Exposures to such leaks were estimated by an analysis of typical domestic water use, quantities of water consumed, and the layout of pipework in typical domestic water systems, coupled with an examination of case reports of catastrophic failures. In addition, various models for exposures in showers and under other domestic circumstances were incorporated into the comprehensive exposure estimates.

Evaluation of the potential health effects from exposure to the lubricating oil used in the pumps required an analysis of the literature on the health effects of mineral oils, and the variation of those effects with type and constituents of the oils. Quantitative comparisons with doses that might cause non-carcinogenic effects showed that leaking oil pumps could not cause such effects. Upper bound estimates were also computed on carcinogenic effects by analysis of the original reports of a skin-painting study of the oil. Lifetime risk estimates for exposures from a leaking pump also turned out to be negligible.