A new study conducted by the American Cancer Society has found that the health consequences of exposure to secondhand smoke are even more far-reaching than we thought.

After following more than 70,000 US adults – who never smoked themselves – from 1992 to 2014, the team of researchers discovered that people who reported being around cigarette smokers during any point of their childhood were 21 percent more likely to die from chronic obstructive pulmonary disease (COPD) than those that had not, after adjusting for the possible influence of a myriad of other health and lifestyle factors.

Those who lived with a smoker for their entire childhood (defined as a stretch of 16 to 18 years) were 31 percent more likely to die from this severe respiratory disease.

These results, now published in the American Journal of Preventative Medicine, are the first to indicate that coming into contact with secondhand smoke (SHS) during the crucial years of childhood and adolescent development can lead to fatal COPD later in life, though past studies have already linked exposure in one’s early years to the onset of COPD as an adult.

“The evidence, with results from this study, suggest childhood exposure to SHS may be the first step in a chain of events that starts with poor lung development and asthma in childhood, leading to development of COPD, and ultimately death from COPD,” the authors wrote.

“Although the analysis focused on mortality outcomes, it should be noted that an association between childhood SHS and adult COPD mortality implies that childhood SHS likely has effects on respiratory disease morbidity in adulthood.”

Indeed, a great number of investigations have also found associations between childhood exposure and an increased risk of developing other lung and cardiovascular conditions, and multiple forms of cancers, both during childhood and later.

 “We need to be aware of the effects of secondhand smoke; they appear to be long lasting. We need to continue to reduce our exposure of it,” lead author Ryan Diver told The Washington Post.

Diver’s team selected their subjects from a larger, nationwide prospective study called the American Cancer Society's Cancer Prevention Study–II (CPS–II) Nutrition Cohort, which included 184,185 men and women, aged roughly 50 to 74 at the time of enrollment. All CPS-II Nutrition subjects filled out a comprehensive survey about demographic, medical, behavioral, environmental, and dietary factors at the beginning and filled out follow-up questionnaires every two years after 1997.

Of the 70,900 participants who met the inclusion criteria for Diver’s analysis, about 52 percent stated that they had lived with a smoker at some time during their childhood, and 74 percent of these individuals had lived with one or two smokers for the entirety of their youth. The authors observed that the proportion of people who had grown up around smokers increased for each birth year – a range of about 1918 to 1942. This makes sense, as cigarettes became increasingly popular as the 20th century progressed, particularly among women.