Beware: Unknown exposure to second-hand smoke may cause early death

Serum cotinine -- a metabolite of nicotine -- when used as a biological marker of exposure to second-hand smoke was found to have associations to overall and cause-specific mortality in non-smokers.

US researchers have identified a new biomarker which revealed that known and unknown exposure to second-hand smoke may lead to an increased risk of mortality in non-smokers.

Serum cotinine -- a metabolite of nicotine -- when used as a biological marker of exposure to second-hand smoke was found to have associations to overall and cause-specific mortality in non-smokers.

Increased levels of serum cotinine in blood were significantly also associated with all types of cancers, and heart disease, the researchers said.

“The study found that non-smokers are exposed to second-hand smoke without even realising it,” said Raja Flores, Professor at the Icahn School of Medicine at Mount Sinai in New York, US.

Non-smoking individuals’ cotinine blood levels accurately determined their exposure and subsequent risk of lung cancer and other smoking-related disease, Flores said.

“Using cotinine level to measure exposure to second-hand smoke has important public health implications, because increasing the scope of smoke-free environments would likely decrease cotinine levels in the general population and ultimately death,” added Emanuela Taioli, Director at Mount Sinai.

The study, published in the journal Carcinogenesis, provides a more accurate way to gauge second-hand smoke exposure.

It also presents a strong case for more stringent limits on smoking and increased preventive screenings for those more likely to have been exposed to second-hand smoke.

For the study, the team examined 20,175 non-smokers. After adjustment for sex, education, race/ethnicity, body mass index, and smoking habits, their analysis showed a significant increase in years of life lost across cotinine concentrations.

In the adjusted analysis, the lowest quartile of cotinine concentration -- below the detectable level -- was associated with 5.6 years of life lost while the highest quartile was linked to 7.5 years of life lost.

A stricter legislation establishing smoke-free areas, together with education efforts in low-income and minority communities, is imperative, the researchers concluded.