Key results from the Lao PDR risk assessment of SPL 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. Dieldrin levels also exceeded the guideline; however, it was not considered a chemical hazard associated with the SPL case study site. There is no record of dieldrin use or storage at the SPL case study site. Dieldrin was only assessed in a single fish caught in a pond down gradient from the workshop. The pond also receives surface run-off water from neigbouring properties, therefore it is possible that it originated from a separate location;
- The receptors identified at the site were both ecological receptors (fish and terrestrial animals) and humans (workers and residents of local homes); and
- Exposure pathways identified were split into onsite exposures, exposures related to oils being transported off site to family homes, and exposures related to off-site migration of contaminants via wind erosion or surface water run-off.
- The exposure assessment used a computer-based model to estimate the total daily exposure of people (workers, family members of worker, local residents and school children) to PCB + dioxin/furan TEQs. The results suggest that dermal exposure to PCB and dioxin/furan contaminated transformer oils is likely the predominant route of exposure, followed by the ingestion of contaminated fish.
- 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 assessed both as carcinogens and non-carcinogens.
- Results of the Risk Characterization suggest that there is a potential human health risk associated with exposure to PCBs and dioxin/furans in transformer oils, contaminated soil/sediments and fish tissue. The PCB exposure calculated using the computer-based model was supported with measured concentrations of PCBs in the blood of workers and wives of workers. However, this potential risk was placed into the context of uncertainties and assumptions made during the risk assessment. Two options were discussed: (1) conducting a refined risk assessment to determine if potential risks are over estimated; or, (2) conduct risk management activities at the site to mitigate potential risks.
Towards Risk Management
The following are the key risk management alternatives recommended by the participants of the National Training Workshop (Vientiane, Laos PDR, 28-31 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 – adopting and enforcing law and regulation controlling POPs.
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.