TORONTO: Children exposed to tobacco smoke in early childhood adopt anti-social behaviour, engage in proactive and reactive aggression, and face conduct problems at school, even drop out at age 12, a research has showed. Exposure to tobacco smoke is toxic to the developing brain at a time when it is most vulnerable to environment input, the researchers said. “Young children have little control over their exposure to household tobacco smoke, which is considered toxic to the brain at a time when its development is exponential,” said lead author and Professor Linda Pagani from the University of Montreal in Quebec, Canada. Parents who smoke near their children often inadvertently expose them to second- and third-hand smoke. Abnormal brain development can result from chronic or transient exposure to toxic chemicals and gases in second-hand tobacco smoke. These compounds eventually solidify and create third-hand smoke. In the study, the researchers found compelling evidence that suggests other dangers to developing brain systems that govern behavioural decisions, social and emotional life as well as cognitive functioning. Anti-social behaviour is characterised by proactive intent to harm others, lack prosocial feelings, and violate social norms. Such behaviours include aggression, criminal offences, theft, refusal to comply with authority, destruction of property and is also associated with academic problems in later childhood. “These long-term associations should encourage policy-makers and public health professionals to raise awareness among parents about the developmental risks of second-hand smoke exposure,” Pagani said. For the study, published in the journal Indoor Air, the team examined 1,035 boys and girls born in 1997 and 1998. Their parents reported whether anyone smoked at home when their children were aged 1.5 to 7.5 years. At age 12, their children self-reported their anti-social behaviour and academic characteristics.