Some workers at oil and gas sites where fracking occurs are routinely exposed to high levels of benzene, a colorless gas that can cause cancer, according to a study by NIOSH.
More than 100 families affected by fracking sent a letter to President Obama recently, asking for him to meet with them and hear about their experiences.
Under a settlement agreement approved last month, the Wyoming Oil & Gas Conservation Commission must adopt more rigorous policies for scrutinizing industry requests to keep the identities of fracking chemicals secret.