That’s the warning from North-East programme for tobacco control, Fresh, as the Secondhand Smoke Is Poison campaign relaunches this week.
It encourages smokers to quit or take it outside, ensuring children and grandchildren are not regularly exposed to smoke indoors.
Figures from the British Thoracic Society in 2016 suggest that one in three children who ends up in hospital with an asthma attack has been exposed to cigarette smoke.
Evidence also shows that adults exposed to secondhand smoke are at increased risk of stroke, coronary heart disease, chronic obstructive pulmonary disease and lung cancer.
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Ailsa Rutter, director of Fresh, said: “No one wants to put their family at risk. However, secondhand smoke is a serious risk to health, spreading around the house and lingering, long after you can see it or smell it. Smoking with the back door or window open does little to protect the family – quitting or taking it completely outside is the only way.”