Imagine you are a nurse working in an emergency room, and a worker on a gas fracking well comes in covered in chemicals used in the drilling process. You call the gas company to find out what chemicals are being used to help in your assessment of possible health risks to your patient, and even yourself, but find out they don't have to disclose this information.
Or, imagine you are a public health nurse in a community with many natural gas fracking wells, and you notice complaints of well-water contamination. How can you assess the extent of the issue without baseline data on water quality or knowledge of the chemicals used in the fracking process?