constant or prolonged exposure2 secondhand or passive smoking can gradually cause partial or total impairment of the cns(central nervous system), lung disorders such as bronchitis, pneumonia, tracheatitis(inflammation of the windpipe), lack of appetite and nausea due to stomach disorders, which inturn lead to lack of nutrition, dehydration and eventually decrease mental and physical inefficiency, nervousness, trembling and since tobacco is addictive, it can lead to eventual addiction of the child itself towards smoking and atlast the most feared of all...... cancers of lungs, windpipe or foodpipe. The damage control can be 4 the responsible parents2 keep the child away from smokers, let the child b aware of the evils of smoking(if the parent or the guardian feels the child is mature enugh2 understand it).. and do not get panicked if u feel the child is showing any symptoms of the disorders mentioned above.... and most importantly, dont let the child panic at any cost!!