While state regulators and the drilling industry say the rules should help resolve concerns about the safety of drilling, critics and some toxicologists say the requirements fall short of what’s needed to fully understand the risks to public health and the environment. The regulations allow companies to keep proprietary chemicals secret from the public and, in some states, from regulators. Though most of the states require companies to report the volume and concentration of different drilling products, no state asks for the amounts of all the ingredients...