[link|http://www.nlm.nih.gov/medlineplus/secondhandsmoke.html|NIH Link Collection].

In particular, [link|http://www.epa.gov/smokefree/pubs/etsfs.html|US EPA]:

Major Conclusions

Based on the weight of the available scientific evidence, EPA has concluded that the widespread exposure to environmental tobacco smoke in the U.S. presents a serious and substantial public health risk.

In adults:

ETS is a human lung carcinogen, responsible for approximately 3,000 lung cancer deaths annually in U.S. nonsmokers. ETS has been classified as a Group A carcinogen under EPA's carcinogen assessment guidelines. This classification is reserved for those compounds or mixtures which have been shown to cause cancer in humans, based on studies in human populations.

In children:

ETS exposure increases the risk of lower respiratory tract infections such as bronchitis and pneumonia. EPA estimates that between 150,000 and 300,000 of these cases annually in infants and young children up to 18 months of age are attributable to exposure to ETS. Of these, between 7,500 and 15,000 will result in hospitalization.

ETS exposure increases the prevalence of fluid in the middle ear, a sign of chronic middle ear disease.

ETS exposure in children irritates the upper respiratory tract and is associated with a small but significant reduction in lung function.

ETS exposure increases the frequency of episodes and severity of symptoms in asthmatic children. The report estimates that 200,000 to 1,000,000 asthmatic children have their condition worsened by exposure to environmental tobacco smoke.

ETS exposure is a risk factor for new cases of asthma in children who have not previously displayed symptoms.

I haven't seen the 38,000 number you mentioned, so I don't know how that was arrived at.

All of these estimates depend on various complicated assumptions and extrapolations. There are error bars on all of the estimates that almost always get dropped when the numbers are reported in the popular press. (E.g., is that 3,000 +/- 50%?)

I'm sure that second-hand smoke has caused disease in many people, and that disease has resulted in death among some of those people. But those deaths are probably much more common in, say, a poverty-level household with small children in a small, cramped, poorly cared for house in the hills (where radon may be common as well) with parents who are chain smokers, than, say, among middle-class people who live in a smoke-free home who very occasionally get a whif of smoke when walking out of a building. In other words, I'm sure it depends on the level of exposure, the genetic predisposition, the overall heath, and the exposure to other hazardous agents.

Distilling it all down to one number doesn't tell a person whether second-hand smoke is more or less dangerous than [link|http://www.cdc.gov/nasd/docs/d001201-d001300/d001273/d001273.html|grilled meat, peanut butter, mustard, beer, bread crusts or breathing air in a mobile home].

HTH a bit.

Cheers,
Scott.