Amos says:"I am not 100% convinced that the occasional whiff of burning leaves is such a harm as all that. Less so, say, than driving a smoggy car."
On the other hand, the World Health Organization says:
"In the US second-hand smoke causes about 3,000 lung cancer deaths a year, compared to less than 100 lung cancer deaths per year from traditional forms of outdoor air pollution.
Second-hand smoke also causes and aggravates asthma and other breathing problems, particularly in children. It is also an important cause of sudden infant death syndrome (SIDS).
While most discussion about second-hand smoke have concentrated on lung cancer and breathing, the effects on heart disease are more important. The chemicals in second-hand smoke poison the heart muscle, interfere with the ability of blood vessels to adjust themselves to control blood pressure and flow, increase the buildup of blockages of blood vessels (which lead to heart attacks), and make blood stickier. The net effect is that there are about 15 times more deaths from heart disease caused by second-hand smoke - 35,000-62,000 deaths annually in the US- as lung cancer.
While the tobacco industry continues to claim that the evidence that second-hand smoke causes disease - particularly lung cancer- is controversial, every independent authoritative scientific body that has examined the evidence has concluded that second-hand smoke causes many diseases (Table 1). Moreover, the evidence that second-hand smoke causes disease is not new. The first studies linking second-hand smoke with breathing problems in children and lung cancer in adults 20 years or more ago and the studies linking second-hand smoke and heart disease are over 10 years old."