If you are concerned about safety and the environmental impacts of pyrocatechol versus hydroquinone, IMO they are pretty much equal.
Both of these substances occur naturally and are ubiquitous in the natural environment.
Neither one appears to be a significant health or environmental risk if handled with reasonable precautions (dumping of massive amounts - like recently happened in China - creates problems). Take a look at the MSDAs for both substances. Also look at their WHO evironmental impact assesments. They are on the internet.