Rising from the Ashes: Smoking Revisited

For over half a century (https://stacks.cdc.gov/view/cdc/53234/cdc_53234_DS1.pdf) we have been aware that Environmental Tobacco Smoke (ETS) is an indoor hazard requiring mitigation. During the first half of that period ASHRAE struggled mightily, but in vain, to develop policies, positions and standards that took that into account. It was not until the turn of the century that the Society began to settle on a set of such documents that it felt honored its vision of being a healthy indoor environment (A healthy and sustainable built environment for all). Science has marched on in the last quarter century and it is now time to take a more forward-looking view. Although tobacco use continues to decline in the West, it continues to be strong in Asia and is growing in Africa. This article will review that history and use recent and important research results to enable an evolution of ASHRAE’s approach to ETS.

Key words: smoking, tobacco, environmental health, harm intensity

If there is any tool that epitomizes the evolutionary rise of human beings, it is the burning of organic matter to create heat or, simply stated, fire. We have used fire for cooking, defense and heating for over 2 million years. Where this is fire there is its companion smoke[1]−which has been the bane of human lungs ever since. Once brought inside, humans learned to control that hazard through ventilation.

Figure 1. Caveman cooking dinner over an open fire. (Shutterstock)

Humans also learned that some smoke was useful in one way or another: Food could be preserved by smoking; some smoke smells good; some smoke has bioactive properties; and many cultures use smoke from the smoldering combustion of specific plants in socially significant ways. Technologies for delivering the desired smoke without flames were developed.

Tobacco, a new-world plant, has been used by Indigenous Peoples for medicinal and religious purposes for over two thousand years. Christopher Columbus brought that most valuable import from the new world to Europe in 1492 where it has been claimed a miracle drug, become a currency, shunned for being addictive, banned for being too stimulating, but in general, used widely ever since. While there are a lot of ways to consume tobacco, the advent of the cigarette rolling machine in the late 19th century began to make cigarettes the most common and accessible.

Figure 2. Native American traditionally smoking. (Shutterstock)

Over the centuries of tobacco use, many Cassandras spoke of the deleterious effects of inhaling hot smoke deep into one’s lungs, but the perceived benefits of tobacco smoking assured that little would be done broadly. That all changed rather quickly when in 1964 the US Surgeon General issued a report concluding that smoking causes a host of diseases, most notably lung cancer. As those hazards were to the smoker, there was no reason for ASHRAE to be involved in the issue.

Figure 3. Environmental Tobacco Smoke includes both side-stream and exhaled smoke. (Shutterstock)

Eight years later, another Surgeon General concluded that Second Hand Smoke (SHS), what we now commonly call Environmental Tobacco Smoke (ETS), was hazardous to those exposed to the smoke of others. ETS was now a source of indoor contamination similar to human bioeffluents, moisture generation and other kinds of combustion sources. This now was very much something ASHRAE should deal with through its ventilation standards and guidelines. The original version of ASHRAE’s standard on ventilation[2] did not take that into account but the committee responsible for updating that standard did.

After due deliberation ASHRAE Standard 62-1981 was published with two very different ventilation rates, depending on whether smoking was permitted in the space or not. The 15 cfm/person (7.5 L/s/person) difference did not have quantitative justification, but was very reasonable engineering judgement given the state of knowledge of the day. Unfortunately, it was not considered reasonable by various tobacco interests.

The tobacco companies did not take kindly to ASHRAE’s foray into mitigating the harm from ETS and used one of their favorite approaches—the courts—to deal with it. Once the massive legal war machine of those companies was unleashed, ASHRAE could not expect to win. Opting for a Peace In Our Time[3] tactic, ASHRAE agreed to withdraw and revise the standard with input from the tobacco companies. The result of this appeasement (or more charitably, tolerance) strategy was ASHRAE Standard 62-1989, which contained a single blended rate that allowed for “a moderate amount of smoking”.

That safe, but technically unappealing solution, was stable for a decade. During that time the Manhattan project equivalents at the US Environmental Protection Agency were hard at work examining the ever-increasing body of data on ETS. In 1993, EPA released a report designating ETS as a Class A carcinogen—the most hazardous kind. This report enabled the “moderate amount of smoking” line to be deleted. ASHRAE Standard 62-1999 could only be applied to non-smoking spaces[4]. ASHRAE had gone from a “tolerant” policy to an intolerant one.

Powered by that declaration, ASHRAE’s policies and positions on ETS (including relevant standards) became more doctrinaire over the next few years. ASHRAE’s current position on ETS leaves little room for advancement. While not unreasonable, it was also not technically satisfying since we know that there must be some amount of ETS that would not be significantly harmful. While we may not know what that level is with any certainty, the current policy feels more like excommunication, discommendation, or shunning than a scientific approach.

In one sense, it was a reasonable thing to do, given the state of knowledge at the time, in a better safe than sorry sort of way. On the other hand, it was not a very reasonable thing for those who wanted to allow smoking—as is common in many parts of the world. ASHRAE was essentially entering the political arena by effectively prohibiting smoking. Many countries who use ASHRAE Standards were not choosing to ban smoking. A solution was (and is) needed to determine what a reasonable amount of smoking is, given local preferences.

Science marches on and we are beginning to have the ability to quantify the harm from ETS and put it in the context of the harm from other contaminants of concern in the indoor environment. As discussed by one of us (Sherman) in the July 2024 ASHRAE Journal,[5] the whole paradigm for how we look at IAQ is evolving.

In the February 2023 ASHRAE Journal and the HOT AIR Podcast, another of us (Jones) describes how the concept of the Disability Adjusted Life Year (DALY) can be used regulate indoor contaminants by determining the exposure of contaminants of concern weighted by their harm intensity (HI). Morantes has gone through the Global Burden of Disease studies and has determined the harm intensities for dozens of common indoor contaminants. Although many of the components known to be in ETS are in that list, Morantes did not give us the harm intensity for it.

Despite the fact that literature has not provided an estimate of the harm intensity of ETS, ETS has been studied extensively through epidemiological, surveys, and laboratory investigations. We have, for example, good information on the Global Burden of Disease (GBD) for ETS as well as a way of quantifying total harm in the indoor environment.

We cannot, however, expect to do so based on summing up all the constituent contaminants or by basing it only a single dominant contaminant of concern: The National Institute of Health has identified over 7000 compounds in ETS, split between the gaseous and (both liquid and solid) particle phases—many known to be quite hazardous. Those gaseous emissions contain compounds such as carbon monoxide, acetaldehyde, methane, hydrogen cyanide nitric acid, acetone, acrolein, ammonia, methanol, hydrogen sulfide hydrocarbons, gas phase nitrosamines, and carbonyl compound. Constituents in the particle phase include carboxylic acids, phenols, water, humectants, nicotine, terpenoids, paraffin waxes, tobacco-specific nitrosamines polycyclic aromatic hydrocarbons, and catechols. Additionally, smoke mixtures are known to chemically and physically evolve over time[6] making it difficult to determine the concentrations of contaminants of concern at the time they are inhaled. Particles, for example, can evaporate, agglomerate, or deposit on surfaces at varying time scales.

We need to step back from those weeds to find a practical approach, which means treating ETS as a (combined) contaminant, whose “mass” is in units of cigarettes smoked (i.e. cigarettes in place of the micrograms we often use for more normal contaminants.) Much of studied research is reported in average per cigarette values and we can make use of those:

·         The WHO[7] has estimated the GBD for ETS to be 11,000,000 DALY/year.

For that same period of time, there were roughly 5 trillion cigarettes produced[8].

·         and a global population of about 6.5 billion people.

·         A cigarette has about 1 g of tobacco that gets burned during consumption. Of which, 14 mg of the burned tobacco winds up as PM2.5[9] in the ETS, although that number evolves significantly over time.

There is a lot more specific data that the health community has produced, but this additional data does not help us determine what we need to know to make practical decisions HVAC-related interventions and impacts. The spot-on data that we need has some holes in it. In this article we are going to use some engineering judgement[10] to fill those holes and see where it takes us, recognizing that the variation in doing so makes our results suggestive rather than definitive.

Let us first look at what this global data tells us about what is happening on average. We see that the harm due to ETS from smoking one cigarette is 2.2 µDALYs. One µDALY loss is roughly equivalent to losing 32 seconds of life, so each cigarette smoked shortens the life of other people by, on average, a little over a minute. The monetary cost of that harm will vary by socioeconomic factors including region. The typically used value of a DALY in the USA is $750,000 [10] which puts the harm at a bit under $1.65/cigarette. Those numbers are also a few years old.

To be clear those numbers are for all the people exposed to that ETS, but not including any direct harm to the smoker. The harm is also the average across the global population independent of the environment. Cigarettes smoked outside will clearly expose people to much lower concentrations of contaminants than in a poorly ventilated space. People in closer proximity to the smoker would be expected to get a larger dose. We expect that there will be a very broad (log-normal) distribution of exposures.

We would like to be able to understand how the harm relates to the concentration of smoke so that we can determine how much harm there is from smoking and how things like changing the concentration of that smoke changes the harm. The existing research has everything we need except the dilution rates during the ETS exposures. For that we are on our own. Our working estimate of the median dilution rate is 15 cfm/person (7.5 L/s/person). This is by far the most uncertain estimate in our analysis, but by using it we can calculate the Harm Intensity to be about 56 µDALY/hour/person/cigarette/m³.

No one, of course, has an intuitive feel what that number means[11]; so, we will go through some examples and comparisons to see if this approach passes the laugh test. (Spoiler: it does.) First, let us consider a residential environment, where one person of the 4-person family smokes 2 packs a day in their 2000 sq. ft. home. Assuming the home was ventilated according to ASHRAE Standard 62.2, we can use the HI to estimate that the smoking adds a bit over 0.5 µDALY/person/hour of harm. That translates into about $4000 per year per full-time occupant.

By comparison Morantes estimates that an ASHRAE Standard 62.2 compliant home, where smoking does not occur[12], has harm from other contaminants of about 2.5 µDALY/person/hour. So the additional harm from smoking is then about a 20% increase in harm to the occupants. They could, of course, decide that was an acceptable amount, but they also have the option of increasing the ventilation by about 25% and reducing the total harm to the non-smoking level. Such an increase is not just during the period of smoking, but throughout the year because it lowers the harm from the all contaminants to offset the added harm from smoking.

The values listed above were for increased ventilation. In principle, air cleaning could substitute, as it does for some specific contaminants such as particle matter. The problem is that ETS, like human bioeffluents, is a complex mixture and we do not have a good way to determine the effectiveness of a (filter or) air cleaner on reducing harm, although it could be used to reduce odor. Acceptable Indoor Air Quality, which is the goal of the 62 standards includes both a heath and an odor acceptability component. The latter issue is important but has not been addressed in this article as the barrier to acceptance has principally been based on health argument. There already exists products on the market to deal with tobacco odor.

Next let us look at the opposite end: a high smoking environment in commercial or institutional buildings. Specifically, a “heavy smoking room”, which is a room in which people go principally to smoke. We can assume that every smoker in there is chain smoking (11 cigarettes/hour) and we use a ventilation rate of 125 cfm (70 L/s) per smoker. Combining that information with our value of HI, we estimate about 3 µDALY of harm per hour a person spends in such a room from the ETS. That translates to about $2/hour of added harm. While smokers may be fine with that, staff or other non-smoking occupants are probably not.

Comparing that to the Morantes value, this situation is about 10 times the harm from the typical conditions. In such a space, one might wish, because of workers, to provide the same level of IAQ in smoking space as the rest of the building, which could be done by increasing the rate and using a mixture of outdoor and transfer air. Of course, that is the whole point of having a harm intensity for smoking. It gives the designer the ability to design for smoking in a way that can provide the same level of health from IAQ that happens in a non-smoking environment…or determine what an acceptable increased harm is for their situation.

It is, however, possible to estimate the amount of additional outdoor air that would be necessary to provide the Morantes level of harm from all sources. That value increases the additional outdoor air rate, per smoker, by roughly an order of magnitude. It takes about 160 cfm/person [9] (80 L/s/person) of outdoor air to provide the same level of health in a heavy smoking room as in a non-smoking space. This result would imply that one could use that same value per heavy smoker in a mixed space.

As a final example, let us look at the notorious “moderate amount of smoking” allowance of the 1989 version of Standard 62. Assuming that one is in a commercial building, having a base rate of 15 cfm/person (7.5 L/s/person) and allowing a moderate amount of smoking (1 cigarette per hour) for that fraction (17%) that smokes we get about 0.4 µDALY of harm per occupant per hour they are in the building. Assuming a normal work schedule (2200 hours/year) we can see that the allowance of a moderate amount of smoking costs every (USA) occupant about $600/year in harm from ETS.

As before could also calculate the increase in ventilation rate that would be necessary to reduce the total harm to the Morantes level. In this case, it is a moderate increase of 15%. One must remember that this is for all the time the building is occupied and for all occupants.

The bar chart in Figure 4 summarizes the results for our example cases.

Figure 4. Each pair of bars indicate the harm due to smoking (orange) and top of the harm from the normal contaminants (blue). The “Adjusted OA” bar that follows each example is the result when the outside air flow has been adjusted to make the total be the same value (2.5 μDALY/person/hour) as the non-smoking situation.

The first stacked bar in Figure 4 is for the case of a heavy smoking room that has an exhaust flow of 125 cfm/person of transfer air. The blue bar represents the non-smoking harm from that transfer air—which is our target level—and the orange bar is the extra harm due to ETS. The following “adjusted OA” bar represents the case where we ventilation the space with outdoor air to reduce the total harm to the target level. This requires about 160 cfm/person and we see that the most of the harm is from smoking. Here the harm from smoking is ten times harm from other indoor sources

The next pair of bars is for the case where there is a smoking in a home. At our example rate that adds a much smaller extra bit of harm, which may or may not be acceptable to the occupants. If they wished to reduce the harm to the target it requires about a 24% increase in outdoor air.

The final pair of bars represents the case of a moderate amount of smoking such as in an office environment. Here the impact is even less than the residential situation and it can be mitigated with a 15% increase in outdoor air. It should be noted than none of these examples has determined whether the resulting odor is acceptable as there is a very wide range in smoking acceptability. Separate communities may be differently accepting and so it would be up to the community or the designer to have limits based on perceived air quality independent of health evaluations.

The values listed above are too preliminary to be used in more than demonstrative form. Rather their purpose here is showing that, although ETS is a complicated, odorous, and carcinogenic substance, it no longer needs to be shunned as though it were weaponized anthrax for which a single iota may be deadly. Rather we now have the means to treat it like other contaminants of concern and design systems that facilitate choice.[13]

ETS researchers would rightly say that the topic is a lot more complex than described herein. There is still a lot of work needed to understand the complexities of the ETS mixture from a physics, chemistry, comfort and health perspective. We currently do not have a practical air cleaning technology that reliably and quantitatively reduces the harm from ETS. Individual variations can be important for certain sub-populations. All of that, however, could also have been said at the turn of century, but a lot of very good work has improved our state of knowledge. We now may enough to make some reasonable estimates of how to handle the indoor environment when smoking is permitted.

This approach described in this article could in theory be incorporated into our IAQ standards (e.g. 62.1 and 62.2) to set rates for when smoking (moderate or otherwise) were allowed. Doing so, unfortunately, is expressly forbidden by the current policies and positions of the Society. The research necessary to advance this cannot happen while the intolerance of the turn of the century remains firm. ASHRAE would need to revise its policies and positions, not to say smoking is good, or that a moderate amount of smoking is OK, but rather to facilitate a rational approach to providing acceptable indoor air quality in buildings where smoking is allowed. It should be up to the community to decide smoking policy, but up to ASHRAE to design HVAC systems accordingly.

Smoking has gone from a Godsend to the Devil’s work several times in history. The truth, of course, lies somewhere in between and depends on social norms. As a professional society caring about acceptable indoor air quality, ASHRAE needs to offer solutions for problems like how to address spaces where smoking is allowed. We have not been able to do that of late, but in the next iteration we should be able to do so.

Notes and references