But schools are also useful agents for changing parental smoking behaviour, the same study concluded.
Researchers discovered that one in three nine and 10-year-olds with smoking parents, had levels of nicotine in their urine equivalent to those found in someone who smokes every day.
"Only 45 per cent of the children in the study showed urinary nicotine levels that correspond to a person who neither smokes nor is exposed to cigarette smoke from others," Dr Julio Kaplan, one of the authors of the study, told an Argentine newspaper.
However, researchers from the Foundation for the Investigation and Prevention of Cancer, known by the Spanish acronym Fuca, were pleased to discover that school-based anti-smoking campaigns were successful in changing the smoking behaviour of a significant proportion of parents.
Levels of urinary nicotine in children were halved after smoking parents attended anti-tobacco lectures in schools and received leaflets and stickers containing anti-smoking messages.
"This study proves that a simple model of school intervention in the family can reduce the exposure to tobacco smoke that children receive in their homes," said Dr Fernando Verra, a Fuca specialist in tobacco-induced illnesses.
The study was funded by Argentina's Ministry of Health which is concerned at the 40,000 deaths nationwide, attributable to smoking each year.
The research was carried out among smoking parents of children aged nine to 10 at three private schools in Buenos Aires, and urine samples from 56 children were examined for nicotine levels.