Legislation giving Massachusetts some of the nation's toughest curbs on smog-causing automobile tailpipe emissions was signed Thursday by Gov. Michael S. Dukakis.

"For the first time in 20 years, we have a fighting chance of cleaning up the air we breathe," said Democratic state Rep. David Cohen, the chief House sponsor the bill."It also has enormous national implications because the action Massachusetts has taken will be a catalyst to spur other states to adopt stricter standards," he said.

The regulations will require manufacturers to reduce tailpipe hydrocarbon emissions by 75 percent and nitrogen oxide tailpipe emissions by 50 percent through the mid-1990s.