A Government discussion paper on relaxing air quality standards shows the changes could mean some people die sooner.
Environment Minister Nick Smith has issued proposals to end bans on some new polluting businesses and allow councils to breach air standards more often.
A study three years ago found 1100 people per year die prematurely from pollution from wood and coal fires, vehicle fumes and factories.
New air standards intended to begin from 2013 were meant to prevent more than 600 of those deaths by 2020.
The discussion paper about changes to the standards shows only about a quarter of those deaths would now be prevented.