ment technologies used by laboratories continue to improve, PFAS are being detected in environmental samples at lower and lower concentrations. A risk assessor who concludes that PFAS are not a concern because they were not detected in an environmental sample may not adequately characterize risk due to the reduced limits of reporting (LOR) and reduced Tier 1 screening criteria currently available. Being prepared for these eventualities is essential when conducting risk assessments for PFAS. Acknowledging the pace of change in available toxicity information and discussing this issue as an uncertainty are musts for completing risk assessment reports. GHD has learned that changes in toxicity information, lab measurement technologies and acceptable levels can understandably promote mistrust, anger and anxiety in the affected community. Being open about these issues when talking with the public, is also essential.
investigating how potential sample contamination may occur by using several types of blank samples in the QA/QC program. Once amounts of the chemicals of concern have been measured in the environment, risk assessors may use mathematical models to determine how the chemicals might move through that environment. For example, such a model might provide an estimate of how much of a chemical would be found in a fish that swims in contaminated water, or how much would be found in a bird that eats that fish. Currently, though, there is a lack of understanding of how PFAS behave in a food chain, although scientists have measured PFAS in birds, mammals and fish. The existing models are thus not reliable, and for risk assessment purposes, it is recommended to measure PFAS in living tissues, rather than trying to use an uncertain and unreliable model.
CONCLUSION “Ultimately, the rapid pace of change in science, technology and government regulations, along with transparency about the challenges at hand, is what makes the risk assessment and management of PFAS an evolving challenge. GHD’s continued approach is to work diligently with the community, government agencies and industry to communicate the challenges of PFAS and to provide risk assessments that can be reliably used to make decisions moving forward,” concluded Collins. For more information, email: ian.collins@ghd.com.
MEASURE ACCURATELY AND DON’T MODEL WHEN ASSESSING EXPOSURE At this stage of a risk assessment project, a risk assessor estimates the magnitude of each exposure to the chemicals. Human exposures and ecological exposures are estimated in the same way, accounting for time spent in the contaminated area, eating crops or garden produce from the area, drinking water, contact with soil, inhaling air, etc. In order to make good estimates of exposure, accurate and precise measurements of the amounts of the chemicals in the environment are needed. Because PFAS are present in many consumer goods, from clothes to food wrappers, as well as some types of sampling equipment, PFAS cross-contamination during sampling or laboratory analyses can be an issue. A robust Quality Assurance/Quality Control (QA/QC) program is an important part of the risk assessment process so the results are reliable and repeatable. For example, GHD has adopted sampling guidelines from Australian governments, such as making sure to wash new clothes at least six times before wearing them to sample PFAS at a job site. In addition, GHD recommends thoroughly www.esemag.com @ESEMAG
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