Biomonitoring analyzes blood and urine samples to determine an individual's level of toxic exposure. Several recent biomonitoring studies showing troubling levels of toxic chemicals present in people have raised concerns among public health groups.

Supporters of SB 600 claim that a state-wide biomonitoring program would have been more useful than individual studies. The bill would have set up a panel of scientists, public health officials, citizens and government officials to determine participants and chemicals that would be researched. For instance, the panel could have selected farm workers and examined exposure to pesticide and insecticide, chemicals with which they routinely work.

The results of this targeted approach could have lead to more protective occupational safety rules for farm workers or laborers in other industries. A healthier population, supporters say, could have saved the state millions of dollars in healthcare costs and environmental remediation.

After three consecutive years of consideration by the California legislature, the bill reached the governor's desk this year for the first time. Groups that supported the bill, such as the Breast Cancer Fund and Commonwealth, have been sharply critical of the governor's veto and have made clear they will work to see the bill reintroduced next year.