Key results from the risk assessment of Cambodia SEDCW case study are:
- The problem formulation indicated that all the components required for a human health risk were present: chemical hazards, receptors and pathways linking the hazards and receptors.
- The chemical hazards identified were PCBs and dioxin/furans.
- The receptors identified at the site were both ecological receptors (fish, crabs, snails and terrestrial animals) and humans (workers and residents of local homes).
- Exposure pathways identified were split into onsite exposures, and exposures related to off-site migration of contaminants via wind erosion or surface water run-off. Exposure scenarios included the exposure of SEDCW workers, students living in dormitories and local residents.
- The risk assessment model indicated that ingestion of contaminated food (e.g., crabs) is likely the predominant route of exposure for PCBs and dioxin/furans.
- Toxicity reference values (TRVs) were selected in order to calculate a numerical expression of potential human health risk. The chemicals of potential concern (PCB + dioxin/furan TEQs) were treated both as carcinogens and non-carcinogens.
- Results of the Risk Characterization indicated that there is a potential human health risk associated with exposure to PCBs & dioxin/furans in transformer oils, contaminated sediments and crab tissue. The PCB exposure calculated using the computer-based model was confirmed with measured concentrations of PCBs in the blood of workers.
The potential risk was placed into the context of uncertainties and assumptions made during the risk assessment. Two options were discussed: (1) conducting a refined (more detailed) risk assessment in an attempt to determine if potential risks are actually negligible or absent; or, (2) conduct risk management activities at the site to mitigate potential risks.
Towards Risk Management
The National Training Workshop which took place in Siem Reap, Cambodia from 19 – 21 January 2009 assessed potential risk management measures which could be applied to reduce the exposure and related human health risks to workers, and local residents. A short list of possible measures was created. Recommended measures included:
The following are the key risk management alternatives recommended by the participants of the National Training Workshop (Siem Reap, Cambodia, 19-21 January 2009):
- Develop and enforce an occupational health and safety plan;
- Monitor and verify effectiveness of mitigation strategies;
- Conduct Risk Communication and Training;
- Undertake measures for controlling and containing PCB Hazards;
- Cap the hot spot surface to control erosion of soil surfaces in the hot spot by rain and wind erosion and off-site transport; and
- Governance – strengthen inter-ministerial coordination unit for POPs, and adopt/enforce law & regulation controlling the use, storage and disposal of PCBs and contaminated equipment/waste.
Given the limited resources and competing priorities, the risk management for the site should focus primarily on clusters of simple and implementable risk management options for the site and more detailed clean-up operations follow later. The emphasis of the risk management should be on capacity building, public awareness and putting in place and enforcing health and safety plan and other emergence prevention and control procedures.
Results of the risk assessment and the risk management recommendations made herein were used in discussions addressing Risk Management during the National POPs workshops (January 2009).