CHEYENNE, Wyo. (AP) — The Wyoming Supreme Court heard arguments over whether a trade secrets exemption in the state's open records law shields many of the chemicals the petroleum industry uses during hydraulic fracturing from public disclosure.

Companies are required to provide the Wyoming Oil and Gas Conservation Commission with lists of the ingredients in the chemical products they use while fracking.

Environmentalists also want to know which chemicals are used. They sued the commission after it refused to disclose any chemicals classified by companies as trade secrets.

The Supreme Court heard arguments Wednesday and will rule in writing later.

Fracking involves pumping water, sand and chemicals into oil and gas wells to open deposits of fossil fuels. Environmentalists say knowing the chemicals used can help landowners test for pollution in their well water.

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