By Natasha Bulowski, Local Journalism Initiative Reporter In the aftermath of a crackdown on benzene pollution plaguing Chemical Valley, environmental watchdogs say another chemical that causes choking, coughing and burning eyes and throats is still abundant. Sulphur dioxide levels in the region, which is home to 67 petrochemical plants near Sarnia, have also been exceedingly high. Levels regularly exceed federal air quality standards despite new regulations passed by Ontario in 2022 aimed at reducing emissions by 90 per cent in the Sarnia area. Sulphur dioxide is a toxic compound released in the refining of hydrogen sulphide, otherwise known as “sour gas,” recognized for its pungent rotten-egg smell. Much of the sour gas refined in the Chemical Valley comes from Alberta crude. It is released when plants flare and while processing…