Second Hand Smoke- Another Bad Study

A study came out of the city of Xian, China showing that people who were followed over 17 years that were exposed to smoke had a higher incidence of heart disease and stroke than those who didn’t.  The numbers in this study were quite small, especially when compared with other larger studies.  This study followed 910 people, as opposed to the 35,000 followed in a California study that showed no link to second hand smoke and disease.

From our hotel room looking into the city of Xian

But what is not stated is what is obvious to any who have lived or worked in China, especially the city of Xian.  The pollution in Xian is far worse than any city in the United States in recent memory.  Any westerner who goes to Xian will wake up with a cough, that will continue until they leave China. The particulate matter in such pollution has a well known, and well correlated rate of heart disease. In fact, the city of Xian has the worst air pollution in China, and often the second or worst in all of Asia.

Air pollution is a mix of gases, liquids, and particulate matter – at far higher concentrations than second hand smoke. There are very good studies that have shown increased risk for cardiac disease, stroke, and lung disease based on exposure to the material.

In China, especially in the growing cities, the pollution is based from coal- with high particulate matter, carcinogenic carbons which lead to increased clotting of blood vessels, increased systemic inflammatory responses, constriction of arteries, and a response that is far worse than noted with second hand smoke.  The American Heart Association has clear scientific statements regarding air pollution, without ambiguity.

Particulate matter has been shown to have a relationship with heart rate.  Even short term exposure to particulate matter (less than 2.5 um) increases the risk of hospital admission for cardiovascular and respiratory disease.  These studies were done in the United States – where particulate matter is far less than in the city of Xian.

This May’s issue of JAMA showed that changes in air pollution levels during the Beijing Olympics were associated with acute changes in biomarkers of inflammation and thrombosis and measures of cardiovascular physiology in healthy young people.

JAMA in May of this year had an editorial “China’s Air Quality Dilemma: Reconciling Economic Growth with Environmental Protection” – May 16, 2012. Vol 307, No. 19.

What it points out is the air quality in Beijing, China, before and after the Olympics.  The simple finding is even the USA’s most polluted city has less particles (2.5 um) than Beijing did during the Olympics. Most cities in the United States have, at their worse have 40 parts per million where during the Olympics Beijing had 70, and 85 after the Olympics.

Another view of Xian- on a good day

To be clear: I am a fan of China, and what they are doing with their air quality. It is clearly improving yearly. Compared to what the US had during the height of our industrial age, China is not only cleaner, but they are working hard to keep it clean. China is the large green giant, planting over 1 billion trees a year, and transforming an economy that was coal based to natural gas and atomic energy. But still its air pollution was described best: I had to smoke a cigar to get clean air while in China (anon).

So when a paper comes out, as in this last edition of Chest, and talks about Second hand smoke exposure in the city of Xian (which has far worse pollution than their capital and has the 2nd worst polluted air in the world),

From the City of Xian – where people routinely wear masks, they think second-hand smoke is the problem

and do not account for the particulate level in the air – this is at best a bad paper.   What that paper did is equivalent to saying that eating tomatoes is bad because all those who ate tomatoes had heart disease and not account that they all were people with hyperlipidemia.

Even those who look at the data, without the perspective of being from China, cannot state that it is proof of second-hand smoke.  Their Relative Risk factors are from 1 to 2.88 (recall the relative risk proving that cigarettes and cardiovascular disease are greater than 20, and that a relative risk of 3 is generally what we want for some indication of causation).

This was another bad study- quoted by Reuters, picked up by the AMA daily News.

China has been recently upset that America has been tweeting about the air quality in China. From Yahoo News:

The United States said Wednesday that its embassies in China would not stop tweeting reports on air quality readings in Beijing and Shanghai, which have annoyed the Chinese authorities. “This is an initiative by the embassy in Beijing, by the mission in China, to convey what we believe is useful information to our citizens abroad,” State Department spokesman Mark Toner told journalists. “It’s primarily directed to American citizens, but in terms of Chinese accessing this information, we don’t have a problem with it.
“We would see it as a model for other missions around the globe to do,” Toner said, adding in the past there had been a similar initiative in Mexico.
He added that despite Beijing’s assertions that it was illegal for foreign embassies to issue their own air quality readings the US embassy had no plans to stop sending out the reports on its dedicated Twitter feed.

China’s cities are among the world’s most polluted, but until recently, official air quality measurements regularly rated their air quality as good — even as data from the US embassy in Beijing showed off-the-chart pollution.
Toner said the Beijing embassy now had some 20,000 followers of its Twitter feed which goes by @BeijingAir, and which said early Thursday that the air quality was “unhealthy for sensitive groups” in the Chinese capital.

Recent photo of Shanghi at Sunset

Bottom line- second hand smoke remains the myth that tries so hard to be proven.


For the most comprehensive article on second hand smoke here.

Secondhand smoke exposure predicted chronic obstructive pulmonary disease and other tobacco related mortality in a 17-years cohort study in China. He, Y., et. al. Chest. 2012 printed online

China’s Air Quality Dilemma: Reconciling Economic Growth with Environmental Protection. Dominici, F, Mittleman, MA. JAMA 2012, 307(19) 2100-2102

Brook RD, Rajagopalan S, Pope CA III,  et al; American Heart Association Council on Epidemiology and Prevention, Council on the Kidney in Cardiovascular Disease, and Council on Nutrition, Physical Activity and Metabolism.  Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association.  Circulation. 2010;121(21):2331-2378

Rich DQ, Kipen HM, Huang W,  et al.  Association between changes in air pollution levels during the Beijing Olympics and biomarkers of inflammation and thrombosis in healthy young adults.  JAMA. 2012;307(19):jpc1200022068-2078

Dr. Terry Simpson About Dr. Terry Simpson
Dr. Terry Simpson received his undergraduate and graduate degrees from the University of Chicago where he spent several years in the Kovler Viral Oncology laboratories doing genetic engineering. He found he liked people more than petri dishes, and went to medical school. Dr. Simpson, a weight loss surgeon is an advocate of culinary medicine. The first surgeon to become certified in Culinary Medicine, he believes teaching people to improve their health through their food and in their kitchen. On the other side of the world, he has been a leading advocate of changing health care to make it more "relationship based," and his efforts awarded his team the Malcolm Baldrige award for healthcare in 2011 for the NUKA system of care in Alaska and in 2013 Dr Simpson won the National Indian Health Board Area Impact Award. A frequent contributor to media outlets discussing health related topics and advances in medicine, he is also a proud dad, husband, author, cook, and surgeon “in that order.” For media inquiries, please visit

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Latest Comments

  1. Rollo Tommasi says:

    Doc – Now I accept you have a right to express your own opinions. But, especially when you are speaking about health issues in a professional capacity, you also have a responsibility to do so in a fair and objective way.

    And your conduct lies far, far short of that standard.

    Why do you continue to cherry-pick one or two studies, instead of presenting an overall picture of the evidence?

    Why do you continue to misrepresent the few studies you do refer to? For instance, why do you claim it is a weakness of the He study that it does not conclude a definitive link, when that is a strength of responsible research? Why do you not point out that, while the report’s findings are not conclusive, they do support and add value to existing research? Why do you not point out that people in Xian all inhale the same air, whether they are also exposed to secondhand smoke or not? Why do you conveniently ignore the fact that the findings of these studies showed a dose-responsive relationship between exposure to second-hand smoke and risk of harm when, although not definitive in itself, this is a strong indicator of causation?

    Even having stretched and misrepresented your accounts of those few specially cherry-picked studies as you have, they still do NOT support any argument that harm from secondhand smoke is a “myth”. So why do you pretend that they do?

    And why have you never provided a proper, objective and scientifically rigorous of the main sources of evidence which DO warn about the dangers of secondhand smoke, such as the 2006 US Surgeon General’s report and the 2004 IARC monograph?

    For a doctor to be presenting views on a health matter in such a prejudiced, ill-informed way as you have is irresponsible and unprofessional.

  2. thedoc says:

    Nothing like ad hominem arguments. Yes the breath the same air- how much and which is what needs to make the study. In terms of Surgeon General Report- That is a statement of belief, and not fact – to quote it would be a logical fallacy as an appeal to authority.
    It is clear about pollution- the type of pollution, what it does- and with a low Relative Risk factor it is impossible to make the conclusions – with the added factor of the pollution it is simply ignoring what we do know about air pollution- and having been there – it is far more noxious than any room I have been in with smokers.
    They do not present a dose response relationship- they make a guess and then use that “best guess” to state it is dose responsive – it is not.
    To prove the null hypothesis is not for me to do- it is those who state second hand smoke is a danger- it is to them to prove it.
    This study not only didn’t prove it on the face of it but it ignored the elephant in the room.
    In terms of your ad hominem attacks on me, and my professionalism – I trust you will refrain from those if you wish to debate on this blog. I welcome your debate, but not personal attacks.

  3. Lynn says:

    Are you saying that second hand smoke does not cause heart disease or are you saying that second hand smoke is not harmful at all? Most info given to new parents states that second hand smoke can cause SIDs as well as asthma in children. Parents of children with broncho-pulmonary displasia are warned not to allow their children to be near smoke of any kind, even from burned toast. Is all that simply over-protection? I personally can’t stand to be around cigarette smoke and either leave or make the smoker leave.

  4. Rollo Tommasi says:

    Thank you for your response Doc.

    You argue that you do not have to prove anything. That is wrong. If your argument had been that evidence about the risks of passive smoking is not yet conclusive, then I might understand your position. But you are not making that argument; you are reaching a firm conclusion. You are arguing that harm from second hand smoke is definitely a “myth”. It is as much your duty to prove the truth of your belief as it is the duty of another scientist who stated that passive smoking is definitively harmful.

    Those principles apply to anyone engaging in debate. But there is a bigger issue for you. Your influence in a debate about a medical subject will be stronger than most people’s, simply because you’re a medical doctor. With that power comes responsibility: it is important that you present your arguments in a fair and objective way, and that does NOT involve providing biased commentaries on a small number of cherry-picked issues which just happen to reflect your personal opinion. It is irresponsible and unprofessional for you to argue strongly that passive smoking is a “myth” and at the same time take the view that it is not up to you to prove that claim.

    If passive smoking were really the “myth” you claim it to be, you would have been able to show that the main evidence for the argument that it is harmful is wrong. I pointed you to the main bodies of evidence for smoking laws across the world – I mentioned in particular the 2006 US Surgeon General’s report and the 2004 IARC monograph. If passive smoking were really a myth, then these reports should be fundamentally flawed. Yet you refuse to critique them. Why is that? Their purpose is exactly the same as the EPA report from 1992: that is, to assess evidence available at that time and draw conclusions from that assessment (which is much more than simply a “statement of belief” which you claim them to be). Curiously, you have already tried to condemn the EPA report in your previous article. So what makes you so interested in a 20 year old report long since consigned to the history books, but so reluctant to discuss more recent and comprehensive assessments of the evidence which have directly influenced smoking laws? The only answer I can see is that you would rather ignore these recent reports because you are unable to provide solid reasons for condemning them – after all, your criticisms of the EPA report do not apply to them.

    As for the He report, it considers whether passive smoking presents risks to health ON TOP OF any risks from inhaling the local air. The participants all breathed the same quality of air, and even worked in the same factory for much of their lives. And the report DOES present a dose response relationship (set out in Table 4). That material reflects feedback from participants, and the report is honest and objective in setting out how strongly conclusions can be drawn about these, including the likelihood and nature of any misclassification. And of course, the report makes no definitive conclusions and only claims to offer additional insight and evidence into the debate about diseases for which passive smoking might increase risk. Of course, as a brand new report, it will have had no bearing on previously made articulations about passive smoking being harmful. So it is utterly bizarre that you are trying to argue that this report in any way supports your claim that passive smoking is a “myth”.

    By the way, I suggest you check a dictionary for the definition of “ad hominem attack”, because I have NOT been doing that. I have criticised your actions, and raised concern about your professionalism insofar as they relate to these actions. I have made no broader criticism of you as a person. And where I have criticised your actions, I have done so in a specific and evidenced way. So please do not play the “ad hominem” card with me – it simply indicates you’re unable to defend your own position.

  5. thedoc says:

    You seem to be stuck in a circular argument but let me try to unravel it for you:
    First, when you state I am unprofessional and prejudice, and criticize my conduct – you attack me, and waive your hands at the argument. When you “raise concern about professionalism” – that is ad hominem. Then, when you use the snide comment to have me look up a definition, that is ad hominem at best, rude certainly, and just not nice (especially on Fathers Day). So when you criticize someone personally, then say I am going to attack your writing – you are making ad hominem.
    The He report does not address air quality – you have no idea how much time any of them spent outside, v inside. You have no idea if they lived in an apartment in town, or outside of town – you have no idea if they heated their apartment with coal (many do) or not. No do you know if the coal in that part of Xian came from the area of higher radiation or not (some do). Those are not minor issues- those are major issues. If you had been there, or lived there you might ask if the factory was located east of town or west of town. So this does not go “ON TOP OF” any air quality- because in that region the air quality can change from one area to the next – all bad, but some much worse. You can have a dose response curve- but gathering it from data that is self-reported does not meet even level one of Evidence based medicine. So does this report offer insight – nope, it muddies the waters.When you have an overwhelming risk of lung cancer, cardiovascular risk, and stroke risk from the air, you cannot dissect out a dose response curve – it is just impossible to do.
    In terms of “reports” or “conclusions” by federal or international agencies – they do not represent bodies of work that are infallible – see my previous discussion about the reports regarding mono-unsaturated fats.
    Let me be clear:
    There is no doubt cigarettes are a health hazard, that those who use them have a huge and well-defined risk of cancer, heart disease, lung disease, and vascular disease. We don’t know the component in that, or combination of components in the smoke, that cause this- but there is little doubt that they have a major issue. That is different than some other forms of tobacco that do not have the same issue – but are assumed to. But there smokers have a relative risk value exceeding 20 – which meets statistical significance of a relative risk greater than 3. This study, as with most studies, do not meet that value.

  6. thedoc says:

    Let me be clear – if you smoke around a child then you are an idiot. Smoke does not cause asthma, but it can make the reactive airway disease worse – and smoking around a child, indoors, is just idiotic and selfish. There is no good evidence second hand smoke causes heart disease – none, zero, zip. I personally believe regulators go too far when they remove the right of private places to allow tobacco. I don’t smoke cigarettes, by the way – never have.

  7. Rollo Tommasi says:

    Thank you for your reply. I stand by my comments, which are not ad hominem and which are focused to your actions in the specific context of this debate. What I have said to you is no worse that you have said about the He report (“this is at best a bad paper”). I am not here to try to ruin your professional standing. So why am I here? It is to get you to either properly justify your strongly stated accusation that passive smoking is a “myth” or adopt a more reasonable tone in this debate. So let’s stop pretending there are circular arguments and discuss this issue in a responsible way.

    In terms of the He study, you are of course entitled to raise the concerns you do and you raise some interesting arguments. My own view is that, having considered the factors you refer to, I am unable to comprehend how they would be enough to account for the different relative risks between those exposed and those not exposed to second-hand smoke, as you’re having to argue that the exposed people would be considerably more affected by your other factors and I struggle to consider how this is likely. But that is all part of the healthy constructive critique of that particular study, so I have no problems there. What I do have problems with is that you use a relatively narrow criticism of a brand new study, which has never been part of the case that passive smoking is harmful, to argue this confirms that passive smoking is a “myth”; especially when you go out of your way to ignore studies which have been far more influential in demonstrating that it is harmful.

    I also don’t understand the point of your last paragraph. Yes, the health risks of direct smoking exceed those of passive smoking. But that doesn’t make passive smoking a “myth”. And a relative risk of 3 or more is both an entirely different issue from statistical significance and not an essential requirement in epidemiology (at least not when drawing conclusions from a large body of evidence, as is the case with passive smoking and lung cancer/heart disease). So I don’t understand why you make that point. Relative risks of considerably less than 3 have been enough to establish, for instance, that obesity can increase the risk of colorectal cancer [1] and anti-hypertensive drugs can reduce risks of stroke [2]. Indeed, you yourself recently reported without any criticism a report in the BMJ about the effects of calcium of heart attack risk, when both the findings for both calcium in the diet and calcium supplements covered Relative Risk of well under 3 [3].

    So why can’t you debate the issue fully and honestly by critiquing the main sources of evidence which conclude that passive smoking is helpful – the most obvious being the 2006 US Surgeon General’s report and the 2004 IARC monograph?


  8. thedoc says:

    With the high background of air pollution you cannot pull out second-hand smoke dose response curves – the background is overwhelming, hence the study is simply nonsense on the face of it. It would be like taking a study of people with high degrees of exposure to the sun who get melanoma and pulling out how many chest x-rays they got and determining the dose response curve of chest x-rays and skin cancer – with a RR less than 3- -not going to happen. You want to take other variables out of the equation and argue about relative risks- much easier to do, but not perfect.

    Also- it is not passive smoking- that is a prejudicial term.

    In terms of epidemiology- there is not a large body of good evidence- that is a logical fallacy called “appeal to popularity,” or perhaps a version of “appeal to authority.” Surgeon General Report is simply not an authority- it is a political entity, and if you wish to go through appeal to authority then believe what you are told by any major body and most of the time you will be fine.

    Otherwise- I suggest I course in statistics, learn to do some research, and learn the difference between good and bad research

  9. thedoc says:

    The original article describing relative risk stated how the statistic should not be used – “Second, the relative
    risk, and hence the corresponding excess relative risk, should be controlled for the influence of other known or suspected aetiological agents which overlap in distribution with the exposure of interest.”

    They missed the most obvious issue with this paper.

    In terms of the question as to second-hand smoke – I continue to await good studies showing that it has a positive association with cardiovascular disease and cancer. There is no doubt that second-hand smoke can exacerbate asthma – and if you smoke around someone with asthma, or around a child – you are simply an idiot.

  10. Second Hand Smoke: Another Bad Study | Sex, Cigars & Booze Lifestyle Magazine
    [...] article was published with permission from the author Dr. Terry Simpson Originally published Your Doctor’s Orders June 15, 2012 « Four reasons not to quit smoking [...]

  11. thedoc says:

    The primary component in the air in China is from their coal based fuel. Wood and coal products were studied quite a bit in Britain as well as China, showing that they are carcinogenic. This is one reason China is leading the world in changing from a coal-based to natural gas based system. Air quality in all the major cities is improving.

  12. Rollo Tommasi says:

    Doc – Let’s see if you let my response stay posted now.

    I am doing my utmost to give you an opportunity to set out your case that harm from secondhand smoke/passive smoking is a myth. You stand by your claim, yet you refuse to offer any meaningful insight against the main evidence that it is harmful. The most you are able to argue now is that “I continue to await good studies showing that it has a positive association with cardiovascular disease and cancer.” Obviously I disagree with your assessment. But even taking your opinion as it stands, that falls a long way short of justifying a claim that passive smoking (which is a legitimate term to use) is a myth.

    You don’t offer any proper critique to challenge the conclusions of the IARC monograph (which you conveniently ignore) and the 2006 US Surgeon General’s report (if its conclusions are as flawed as you would have us believe, you should be able to tell the world why, rather than trying to hide behind an accusation that it is a political entity). In short, far from me appealing to authority, it is you appealing to conspiracy theory.

    And at the same time, your frustrations at being caught out shine through. For example, saying I need to better understand epidemiology when it is you who confuses “statistical significance” with “relative risk” and who wrongly applies a fixed minimum threshold to relative risk…..when it suits your argument.

    So please do all your readers a favour. If you really believe harm from secondhand smoke is a myth, show us your best criticisms of the main arguments of those who disagree with you.

  13. thedoc says:

    You seem to have a few issues in the wrong orientation.

    The hypothesis is that second hand smoking is harmful – it is not that second hand smoking is a myth. Second hand smoke does exist. When you say the “main evidence that it is harmful” you present no evidence, nor is there good evidence of this. See the previous post.

    Lets go to the IARC monograph – which you seem to hold in such high regard. This is not primary research – this is a monograph outlining some of the research – The conclusions are based on findings of chemicals – either markers like Cotinine. Lets be clear Cotinine is not carcinogenic, it is a marker for nicotine (nicotine is present in our bodies and we use it as a neurotransmitter).

    Or here: The exposure of experimental animals, primarily rodents, to secondhand tobacco smoke has several biological
    effects that include (i) increases or decreases in the activity of phase I enzymes involved in carcinogen
    metabolism; (ii) increased expression of nitric oxide synthase, xanthine oxidase and various protein kinases;
    (iii) the formation of smoke-related DNA adducts in several tissues; and (iv) the presence of urinary biomarkers
    of exposure to tobacco smoke.

    First, those are normal biologic pathways in all animals and that one has an increase in those pathways does not mean it leads to cancer. Those are pathways we all have in cellular function, and all of those pathways are used in our body in cell division. They are also used in cancer cells, and some have higher levels than others.

    Second- these are studies done in animals exposed to high levels of mainstream and sidestream smoke – much higher than in an average room that an adult would be in. But even with this the conclusions from those experiments leads to this conclusion regarding animals:
    There is limited evidence in experimental animals for the carcinogenicity of mixtures of mainstream
    and sidestream tobacco smoke.

    Now to the surgeon general report- again, a report which is not a science paper- but a group of studies about second hand smoke. Most of which, if read individually, conclude that there is no prediction about what these levels mean – and on that basis the surgeon general concluded there is no safe level of second hand smoke. Which is, on the face of it, silly. If you wish to see a similar study- look at the previous study which was done about what good and bad fats are that we talk about here.

    Two final points: I don’t believe in any conspiracy- so please do not ascribe that straw man argument to me. Meta analysis is, in medicine, filled with many issues and often the points of the meta-analysis have proven to be incorrect. NEJM has a great article about that. So, while I don’t believe in conspiracy, there is clearly investigator bias – especially when it is applied to meta analysis.

    Your snarky comments about statistics are incorrect – and if you wish to have a meaningful discussion, either show your point, but don’t attempt to be snarky – it just is rude.

    Final comment: smoke is a risk factor for many diseases,and I don’t deny that it is. I don’t smoke – my brother died of lung cancer from years of smoking, and had heart disease from it, as does my father. One has to define risk in terms of amount- which is where every study has the issue. To state that there is no safe level of second hand smoke is silly. Every chemical, every series of chemicals – other than this one -has levels that are “acceptable” and levels that are toxic. That goes for cyanide in drinking water to salt. To state that second hand smoke is a health risk as much or almost as much as smoking is not supported for cardiovascular disease, or lung cancer – to make those assertions work, you have to greatly multiply the dose. I don’t like being around second-hand smoke at all – but that is because I find it noxious to my nose.

  14. Rollo Tommasi says:

    Thanks for your reply Doc. I’ll consider what you say and come back in the next 24-48 hrs.

  15. Rollo Tommasi says:

    Hello again Doc. As promised, my response to your latest comments.

    1. Are You Arguing Second-Hand Smoke is a “Myth” or Not?

    In your latest post you say, “The hypothesis is that second hand smoking is harmful – it is not that second hand smoking is a myth.” Certainly your arguments do NOT support any assertion that harm from secondhand smoke is a “myth”. And indeed a true “skeptic” which you claim to be would need a lot of convincing either that passive smoking is “harmful” or a “myth”. But in your article you conclude “Bottom line- second hand smoke remains the myth that tries so hard to be proven.” And of course, you’ve previously written an article called “The Myth of Second Hand Smoke”.

    2. Your Critiques of the IARC Monograph and the 2006 US Surgeon General’s Report

    Thank you for at least beginning to critique these reports. But I have a number of responses…..

    You argue that neither report is “primary” research. I do not understand the significance of the point you are trying to make. Both reports provide thorough and professionally conducted assessments of existing evidence – largely the results of primary research – about whether secondhand smoke is harmful or not. That is exactly what they should do and the reports are all the more compelling for that. It is just the same as if I were your patient and was unwell, I would expect you to consider every symptom I was presenting with and all my relevant circumstances before arriving at a diagnosis. I simply do not understand why you would advocate not considering all robust and relevant evidence available.

    Then there are your comments about the reports themselves….. Let’s start with the IARC report. This is what it concluded:

    There is sufficient evidence that involuntary smoking (exposure to secondhand or ‘environmental’ tobacco smoke) causes lung cancer in humans.
    There is limited evidence in experimental animals for the carcinogenicity of mixtures of mainstream and sidestream tobacco smoke.
    There is sufficient evidence in experimental animals for the carcinogenicity of sidestream smoke condensates.

    “Sufficient evidence” is IARC’s highest classification for strength of evidence. “Limited evidence” is its second highest classification, meaning a causal interpretation is considered credible, but confounding factors cannot not be ruled out.

    In your remarks, you refer only to the middle conclusion. You completely ignore the first and third conclusions. WHY WOULD YOU WANT TO DO THAT if you are trying to represent that report fairly? And your claim that “The conclusions are based on findings of chemicals” is totally wrong – the findings are based on a lot more evidence than that. All you discuss are limitations in how one part of the evidence can be interpreted, whipping those limitations to the max while ignoring most of the other evidence.

    I also don’t accept your comments on the USSG’s report. Individual studies on passive smoking and lung cancer / heart disease do not “conclude that there is no prediction about what these levels mean”. The results of the large majority of them are suggestive that passive smoking is potentially harmful, but they cannot offer conclusive proof as individual studies. Meta-analyses are well-established and appropriate ways of testing what conclusions (if any) can be drawn from individual studies. I’m not familiar with the NEJM article you refer to. But I do know that NEJM recognises the validity of meta-analyses and often publishes them – e.g. He et al (1999) which concludes that studies into links between passive smoking and heart disease show it is harmful. Other meta-analyses into passive smoking and lung cancer/heart disease also consistently show harm – e.g. Hackshaw et al (1997), Law et al (1997), Taylor et al (2007). All of which were responsibly undertaken. Your argument on meta-analysis seems to be limited to “Meta-analysis needs to be undertaken carefully THEREFORE no meta-analysis on secondhand smoke can be trusted”. That is clearly a nonsense position.

    3. Your Accusations Towards Me

    I hope you are able to take a step back and look dispassionately at my reference to conspiracy theory and my supposedly “snarky comments about statistics”. If you do, perhaps you will realise you are in no position to complain to me. My comment about conspiracy theory was a direct response to your accusation that I was “appealing to authority”. And I didn’t make the comment in order to be mean. I made it because I wanted to engage in a proper discussion with you but you refused to focus seriously on the “main evidence” I had referred to – the IARC monograph and US Surgeon General’s report. I am pleased you have now at least started to critique these reports.

    Likewise, the real “snarky comments about statistics” came from you when you said “Otherwise- I suggest I course in statistics, learn to do some research, and learn the difference between good and bad research”. That was your charming response to my evidenced point about how relative risk and statistical significance should be interpreted. I see you still have no proper answer to my points on these.

    I look forward to your reply.

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