sentence1: For example, adjusting for age differences between subjects in the economic studies and those affected by air pollution may imply the need to adjust the $6 million VSL downward, but the involuntary nature of air pollution-related risks and the lower level of risk-aversion of the manual laborers in the labor market studies may imply the need for upward adjustments.
sentence2: Pollution related risks are fixed and unchanging in relation to age.