Guidance value assessment 76

The ultimate goal in food safety is to protect public health, which sounds like a clear target. If there is a risk, it must be either avoided or diminished using regulatory measures. The literature review introduced several commonly used guidance values, such as TDI and allowable maximum concentrations. In order to fulfill the safety need, these evaluations often use worst case scenarios. The aim is to ensure that even sensitive individuals are on the safe side. Notably, guidance value assessments typically include several built in worst case scenarios, for example safety factors in dose-response functions and worst case scenarios in exposure assessments. The extreme end would be aiming at zero risk, which is almost in every case unrealistic, but still it tends to be a desired option. As an extreme example, there tends to be no public acceptance for radiation exposure from nuclear power plants, no matter how improbable the hazard (Slovic 2000).

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human health effects and decision making A major challenge in giving fish consumption recommendations and guidance values for the public is that the health effects of beneficial and harmful substances are very much age-dependent. This makes clear and transparent communication challenging. For example, children and unborn children are more vulnerable to developmental defect risks due to MeHg and dioxin/PCB intake, whereas senior citizens would need to worry less about exposure to these pollutants but should try to ensure sufficient intake of omega-3 fatty acid in order to gain the cardiovascular health benefits. The official recommendation acknowledges children and pregnant women as a special population subgroup but closer speculation on age-specific fish consumption is not included in the recommendation. However, according to Finnish fish consumption recommendations by EVIRA, consumption of some fish species typically high in MeHg are suggested to be avoided during pregnancy. Exclusionary fish consumption recommendations like these were also suggested by Mozaffarian and Rimm (2006).

Results in Leino et al. (2013b) provide an example of information production for risk management purposes by presenting concentration information in human tissue. This tissue could be e.g. fish, hair, blood or any tissue with relevance in estimating health outcomes. Not much is known about fetal exposure to pollutants, but many xenobiotics can be transferred through placenta to fetal circulation. Therefore, placenta acts as a biomarker of fetal exposure, particularly important for pollutants with developmental toxicity, such as dioxins and PCBs. Guidance value method assumes that under a threshold concentration, typically set by an international body, the risk is negligible and above the threshold there are needs for actions in protecting the public. This brings us back to the question, "what is safe enough". Generally, lifetime risk of one case in a million is considered to be acceptable, even for the fatal outcomes. This is obviously a policy choice, not a scientific fact.

Another feature in determining the acceptable level of exposure is to add safety margins for no-adverse-effect-level (NOAEL). This approach originates from threshold concentration approach of adverse health effects, where below sufficiently low level exposure the expectation is to see no effects. In no threshold linear dose- response relationship approach even the smallest exposure increase the probability of adverse health effects. This is often the approach taken but there is no scientific evidence about what it has achieved in terms of risk reduction.

There is no way to decide on adequate safety margins scientifically – again, this is a policy choice. Therefore, in some cases limit values may be modified due to societal need and additional considerations. Guidance values set by the WHO and the U.S.EPA are examples of limit values but for example the EU legislation in outdoor fine particles varies because in the more polluted areas reducing concentration levels below the health based limit value becomes economically or politically not plausible (IIASA 2006). This is an example where other interests drive the decision making. An example related to fish consumption is described in Leino et al. (2008) where Finland was granted an exemption to sell fish exceeding

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human health effects and decision making the dioxin limit value because public health effects of BRA were considered to outweigh the risks. Also other interests and needs might have played a role in this decisionmaking.

Measuring concentrations in the environment and comparing the levels against the established guidelines and RFDs has the advantage of being simple and practical for regulatory purposes. As Oken et al. (2012) stated, clear and simple guidance are necessary to result in desired changes. Guidance value assessment answers this need. Karjalainen et al. (2013) used guidance value assessment in analyzing MeHg risk in children. For the majority, U.S.EPA reference dose was not exceeded but for a proportion of children (6-years-old girls and boys being the highest exposed age groups), long-term mean daily MeHg intake estimates exceeded the reference dose. This calls for further studies or actions.

Comparing guidance values to measured concentrations gives a general idea if there are health risks but it does not predict the number of health effects related to the exposure. Actually it is pretty close to the first part, hazard identification, in the traditional risk assessment approach, proposed by the NRC (1983).