Texas regulators have adopted rules requiring oil and gas drillers to disclose on a website the chemicals they use in hydraulic fracturing operations.
The Texas Railroad Commission adopted rules Tuesday to enforce a law passed by the Legislature earlier this year.
Texas has been a pioneer in efforts nationwide to force drillers to be more open about chemical-laced water pumped into the ground to crack dense rock formations to withdraw oil and gas.
The process is known as fracking and some environmental groups fear the chemicals could taint water and pollute the air.
Texas will require companies to disclose chemicals but not concentrations. Other states, such as Colorado, require disclosure of concentrations.
Beginning Feb. 1, the companies in Texas must list the chemicals on a national registry, www.fracfocus.org.