The team studied skin samples from 14 smokers and 19 non smokers. Volunteers had patches of buttock skin irradiated with ultraviolet light to see if this induced the formation of MMP-1. Previous laboratory studies had indicated a link between the enzyme and sunlight. They found that some volunteers not exposed to ultraviolet radiation had unusual amounts of MMP-1 in their skin. Checks showed these participants were smokers.
Tobacco smoke contains thousands of chemicals.
It's very hard to know which ones are active. He hoped to see a further, more detailed study.