Smoke, Fire and Human Evolution

Aug 12, 2016

By Steph Yin

When early humans discovered how to build fires, life became much easier in many regards. They huddled around fire for warmth, light and protection. They used it to cook, which afforded them more calories than eating raw foods that were hard to chew and digest. They could socialize into the night, which possibly gave rise to storytelling and other cultural traditions.

But there were downsides, too. Occasionally, the smoke burned their eyes and seared their lungs. Their food was likely coated with char, which might have increased their risk for certain cancers. With everyone congregated in one place, diseases could have been transmitted more easily.

Much research has focused on how fire gave an evolutionary advantage to early humans. Less examined are the negative byproducts that came with fire, and the ways in which humans may or may not have adapted to them. In other words, how did the harmful effects of fire shape our evolution?


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26 comments on “Smoke, Fire and Human Evolution

  • Here is what Sam Harris has to say about wood fires. I think this is dated 2/12/12 from his blog.

    https://www.samharris.org/blog/item/the-fireplace-delusion

    -Quote from that blog post-

    Here is what we know from a scientific point of view: There is no amount of wood smoke that is good to breathe. It is at least as bad for you as cigarette smoke, and probably much worse. (One study found it to be 30 times more potent a carcinogen.) The smoke from an ordinary wood fire contains hundreds of compounds known to be carcinogenic, mutagenic, teratogenic, and irritating to the respiratory system. Most of the particles generated by burning wood are smaller than one micron—a size believed to be most damaging to our lungs. In fact, these particles are so fine that they can evade our mucociliary defenses and travel directly into the bloodstream, posing a risk to the heart. Particles this size also resist gravitational settling, remaining airborne for weeks at a time.

    Once they have exited your chimney, the toxic gases (e.g. benzene) and particles that make up smoke freely pass back into your home and into the homes of others. (Research shows that nearly 70 percent of chimney smoke reenters nearby buildings.) Children who live in homes with active fireplaces or woodstoves, or in areas where wood burning is common, suffer a higher incidence of asthma, cough, bronchitis, nocturnal awakening, and compromised lung function. Among adults, wood burning is associated with more-frequent emergency room visits and hospital admissions for respiratory illness, along with increased mortality from heart attacks. The inhalation of wood smoke, even at relatively low levels, alters pulmonary immune function, leading to a greater susceptibility to colds, flus, and other respiratory infections. All these effects are borne disproportionately by children and the elderly.

    -end of Sam’s blog post-

    Here in the burbs of Boston, every other house has a fire pit in the back yard. It’s a popular past time now for the family and friends to sit around the fire pit at dusk and into the night talking. There’s no actual cooking going on except for kids roasting marshmallows occasionally. But Sam is right about the wood smoke. It fills my house from the next door neighbor and from another neighbor that I can’t quite locate. I’ve gone out walking around the neighborhood peering into backyards searching for the offender. Can’t find them.

    These fires are permitted for outdoor cooking. No one cares about the cooking part anymore because it’s now a social event tied in, as Sam points out, with wholesome family gatherings. I’m now in the position to be the neighborhood mean bitch when I point out that as an asthmatic they could cause me to end up in the hospital for respiratory therapy all because they have some vestigial attraction to sitting around a fire and socializing. What do they think, that the smoke from that fire shoots straight up to the stratosphere and not a single particle enters their neighbors’ houses?

    I’m pretty sure the general public is unaware of how damaging smoke is for us to breath. My own respiratory problems started from growing up in a household full of cigarette smoke 24/7. My doc says I never had a snowball’s chance in hell of having normal lungs.

    We don’t need fireplaces and we can be good wholesome loving families (if that’s your goal) without sitting around a fire pit out back that is belching toxic smoke.

    My fellow humans, please, let’s get over the smoke and fire thing and move on. We’re not in the pleistocene any more!



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  • While wood smoke produces fine particulates and carcinogens, if coals or rubbish is included in the mix, Sulphur-dioxide and other pollutants are also produced.

    One way which biologists have used for decades, is to use Lichens as bio-indicators of pollution levels.

    http://www.air-quality.org.uk/19.php

    Coal fired power stations produce a lot of sulphur dioxide and mercury pollution.



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  • @ #2 – my fellow humans … we’re not in the Pleistocene any more

    Still a very primal urge, fire building, embers are mesmerizing. Would females be just as happy with “fake” indoor / outdoor fireplaces (for ambience only).

    Native American teepee pole and fabric configuration for smoke release is ingenious, and cozy.



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  • 4
    Pinball1970 says:

    totally got the wrong end of the stick on this, I thought it would be about more evidence of early humans/hominids using fire!

    Info thats useful anyway I always knew BBQ and wood fires were not good for me.

    This paper belwo is five years old now and I looked it up for the techniques rather than the findings at the time but note it mentions no evidence of wood used for the fire.

    It suggests leaves and other lighter organic material was used instead. Like said its 5 years old so there will be more recent papers on this.

    http://www.pnas.org/content/109/20/E1215.long



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  • bonnie

    (for ambience only).

    So the Milky Way, breeze rustling through the leaves, chirping frogs and love songs of a myriad of wonderful woodland creatures isn’t enough ambiance for us? I think we’re gonna be just fine, even better, without the fire.



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  • From the Times article above:

    Fire is even tied to the rise of patriarchy — by allowing men to go out hunting while women stayed behind to cook by the fire, it spawned gender norms that still exist today.

    I read the book mentioned above Catching Fire: How Cooking Made Us Human by Richard Wrangham. In that book he also promotes the idea mentioned above, that men went out hunting and women sat around the campfire cooking and waiting for their men to get back with the meat. I hate this imagery.

    First of all, I don’t believe that a band or group of any size (except for modern day nuclear families) have one guy out hunting and one woman at home cooking for him and their own children. In an extended family this is extremely inefficient and too expensive. In the third world extended families there is one or two middle aged women who run the kitchen. Younger women and teens do the prep work. This type of crew can easily prepare a meal for ten people while the rest of the women are busy at other tasks. There is no way a bunch of guys would come home from a hunt with a load of meat and split off into nuclear family groups, all with their own hearths and make separate meals. I’m not buying that.

    Secondly, what if men on a hunt butchered an animal right where they killed it and cooked some or much or all of it right on the spot? What if some women were along on the hunting party to help with this task and to collect and prepare the hides and to help carry meat back? Seems efficient. If they were hunting a fair distance from camp and needed to transport meat for some distance, wouldn’t it make sense to roast the whole thing right there so it would keep better for the distance home? I wouldn’t want to be walking twenty miles though territory of large predators carrying smelly rotting meat. Something may come after the meat and take me with it too.

    Wrangham’s imagery of nuclear family in the pleistocene is way too reminiscent of Wilma and Fred Flintstone.



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  • Laurie

    There is a more recent version of the same thing and it explains it more as the tribe carry out the steal. They are very experienced in the steal and the approach is very important. They must stay together in formation for it to work and it seems to. Lion whisperer’s.



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  • The article is long on speculation and short on facts. As far as I can tell it is essentially a puff piece that adds nothing new to our understanding of the role of fire in human evolution.

    Regarding LaurieB’s post I have two comments.

    Sam Harris is incorrect in his contention “There is no amount of wood smoke that is good to breathe. It is at least as bad for you as cigarette smoke, and probably much worse.”

    As a retired healthcare professional specializing in the treatment of cardio-pulmonary disorders, I can say there is no scientific evidence to support these exaggerated statements. For example, wood smoke does not contain much, if any, nicotine, one of the most deadly of poisons. For this reason, cigarette smoke (first and second-hand) is far more deadly than smoke from wood fires.

    This said, wood smoke is a very real health hazard with many adverse effects. But like everything else, it is generally harmless in moderation. So enjoy your campfires and cozy fireplaces just so long as you obey civil “burn day prohibitions” and open fire restrictions in our national forests.

    LaurieB also writes: “There is no way a bunch of guys would come home from a hunt with a load of meat and split off into nuclear family groups, all with their own hearths and make separate meals. I’m not buying that.”

    This would no doubt be a great surprise to the many Native American tribesmen and women. For example, it was common for the men of plains tribes to hunt in groups (for a variety of reasons). On returning to their camps, they would divide the meat, and retire to their individual domiciles for the food to be cooked and eaten. There are exceptions to this like the great buffalo hunts, but that is a different story.



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  • I would imagine that burning wood offered far more benefits than hazards to humans. It helped to extend our range into colder climates. Cooked food is easier to process by the human body. Probably used as protection. I would bet that fires helped foster community, in that people socialize in close proximity. Given the average lifespan of our ancestors, smoke was probably not a huge factor in mortality.



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  • Jim L #10
    Aug 15, 2016 at 11:03 pm

    This said, wood smoke is a very real health hazard with many adverse effects. But like everything else, it is generally harmless in moderation. So enjoy your campfires and cozy fireplaces just so long as you obey civil “burn day prohibitions” and open fire restrictions in our national forests.

    Restrictions on campfires in forests, are not only based on the risks of starting forest fires, but also because the heat cooks the tree roots which are below the fire, leaving them open to bacterial and fungal infections which spread into the live wood, to damage or kill the trees.



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  • Alan4discussion writes: “Restrictions on campfires in forests, are not only based on the risks of starting forest fires, but also because the heat cooks the tree roots which are below the fire, leaving them open to bacterial and fungal infections which spread into the live wood, to damage or kill the trees.”

    Prescribed (aka “controlled”) burns of large areas of forest are common in our national forests. As it turns out the past century of fire prevention has been detrimental to forest health, and led to many of the major, destructive, wild fires that have become so common. The National Forest Service and National Parks now use fire to rehabilitate or restore a natural ecosystem that improves forest health, encourages growth and propagation of indigenous species of trees and plants, and reduce the risk of wildfire. Given favorable conditions wild fires are “controlled” for the same reasons. Recently a smallish wild fire not far from my house that might have been easily extinguished was allowed to burn (under control) in order to restore habitat to about 20,000 acres of forest and grasslands. A few minutes perusal of the NFS website will confirm the use of prescribed and controlled burns as an important tool in the effort to re-establish and maintain healthy forests.



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  • Jim L #13
    Aug 16, 2016 at 11:00 am

    Alan4discussion writes: “Restrictions on campfires in forests, are not only based on the risks of starting forest fires, but also because the heat cooks the tree roots which are below the fire, leaving them open to bacterial and fungal infections which spread into the live wood, to damage or kill the trees.”

    Prescribed (aka “controlled”) burns of large areas of forest are common in our national forests. As it turns out the past century of fire prevention has been detrimental to forest health, and led to many of the major, destructive, wild fires that have become so common.

    It very much depends on the type of forest and the time-scale of burning events.

    Indeed in hotter drier climates where the was periodic natural burning, prior to development, human restriction on fires to protect property which has now been built in these areas of natural wild fires, has led to a progressive build up of dry and dead under-brush of highly combustible material, which is essentially a disaster waiting to happen.
    While building in such areas is risky, the best option is small controlled burns, when there is some dampness and not much wind, IF this build-up up of combustible material has been allowed to happen.

    Near property it is better to clear and cultivate the ground to make fire breaks, or keep a dense tree canopy to suppress undergrowth, clear any brashings or other combustible material, and regularly remove small areas of harvestable timber, to have new trees renew the succession of growth, so as to provide a varied range of habitat maturity across the larger forested area.

    The forests and woodlands I was referring to, are the cooler temperate ones ones which do not have natural cycles of burning, but which can be burnt by careless humans starting fires in the dry summer drought periods which are becoming more common due to global warning and climate belts moving towards the poles.

    Lighting a fire over any shallow roots of plants, can leave “cooked material” to rot in the ground and promote infections which spread to live plants in the following months or years. – Plants or trees, which we do not want to be diseased or killed.

    Large scale burns usually happen on a much longer time scale of decades.

    I hope this clarifies some of the points.



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  • ” Fire is even tied to the rise of patriarchy — by allowing men to go out hunting while women stayed behind to cook by the fire, it spawned gender norms that still exist today.”

    I would suggest this is arrant nonsense. In hunter gatherer societies men hunt because they’re stronger and faster (and hunting is macho and exciting) and women gather. However hunting is a very hit and miss exercise with a low success rate and it’s the women who normally bring back the bulk of the calorific intake on a daily basis. On that basis it would make more sense for the men to stay and cook while the women find the food.

    Societies are patriarchal because men are bigger and stronger! Nowt to do with fire.



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  • Below are 18 reasons why wood burning should be banned in all urban areas, from Utah Physicians for a Healthy Environment.

    All air pollution is not created equal. Wood smoke is the most toxic type of pollution in most cities, more dangerous than auto pollution and most industrial pollution. Lighting a wood fire in your house is like starting up your own mini-toxic waste incinerator.
    Lifetime cancer risk is 12 times greater for wood smoke compared to an equal volume of second hand cigarette smoke.
    Burning 10 lbs. of wood for one hour, releases as much PAHs (polycyclic aromatic hydrocarbons) as 35,000 packs of cigarettes.
    Toxic free-radical chemicals in wood smoke are biologically active 40 times longer than the free radicals in cigarette smoke.
    Wood smoke is the third largest source of dioxins, one of the most intensely toxic compounds known to science.
    The very small size of wood particles make them seven times more likely to be inhaled than other particulate pollution.
    Wood smoke easily penetrates homes of neighbors creating concentrations up to 88% as high as outdoor air.
    If you smell wood smoke, you know you are being harmed. The sweet smell comes from deadly compounds like benzene. Once you can smell the smoke you know the concentration of particulate matter is dangerously high.
    The most dangerous components of air pollution are much higher inside homes that burn wood than non-burners, as much as 500% higher. The characterization of a wood burning ban “punishing the little people” is easily undermined because a ban would actually benefit the burners themselves more than anyone else, especially their own children
    Considering the most dangerous part of particulate pollution, wood burning produces as much overall as all our cars during the winter.
    We require emissions testing of all our cars. Great. An average house heated with wood emits about as much winter time pollution as driving between 90-400 cars all winter, but we don’t emissions test wood stoves. Why not?
    The inhalable particulate pollution from one woodstove is equivalent to the amount emitted from 3,000 gas furnaces producing the same amount of heat.
    Emissions from modern combustion appliances for wood logs may increase ten-fold if they are not operated appropriately, and most of them are not.
    Wood smoke is the only pollution emitted right where people spend most of their time. It disperses poorly, is not evenly distributed and stays in the air longer because of its small size. Concentrations can be 100 times higher for neighbors of wood burners than what is captured at the nearest monitoring station. Real local “pollution victims” are created even when overall community levels are low.
    If your neighbor is a regular wood burner, and follows all the rules, i.e. doesn’t burn during yellow or red alert days, but does during all “green” days, you can go an entire winter without having one single day of clean air.
    According to California’s Bay Area Air Quality Management District, burning wood costs the rest of the community, primarily your next door neighbors, at least $2 in extra medical expenses for every lb of wood that you burn. An average fire then costs your neighbors about $40.
    Long ago most communities passed ordinances protecting people from second hand cigarette smoke. Ironically those laws protect people at places they don’t necessarily have to be (restaurants, stores, buildings, etc). But in the one place they have to be, their home, they have no protection from something even worse—wood smoke. People should have just as much protection from wood smoke as from cigarette smoke and for all the same reasons. We don’t allow people to blow cigarette smoke in your face, why should we allow people to blow wood smoke into your home?
    Wood burning is not even close to carbon neutral over the short term, the next few decades, and it is that time frame that will make or break the climate crisis. Burning wood is extremely in inefficient. Per unit of heat created wood produces even more CO2 than the fossil fuels do. Furthermore, the black carbon particulate matter released enhances the absorption of radiant heat in the atmosphere, making global warming worse, and prematurely melts already imperiled mountain snow pack.



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  • Petey #16
    Sep 10, 2016 at 5:43 am

    While some of these items are clearly real and well known risks, – particularly those of medical claims and urban pollution;-
    I think we would need some links to credible research for others.

    The end of this list looks like a rather jumbled list of negative biased reporting with some highly questionable claims.

    Wood burning is not even close to carbon neutral over the short term, the next few decades, and it is that time frame that will make or break the climate crisis.

    That would be so if it was depleting the carbon bank of mature forest, but would be incorrect if it was applied to timber grown for cyclical harvesting.
    It would also be carbon neutral and beneficial to humans if it removed and burnt scrub material from dry areas, where there is a cyclical of build-up of combustible material and periodic wild fires.

    Burning wood is extremely in inefficient.

    That would depend on the type of stove or boiler, and the source of the wood, although wood burning does produce more steam in the exhaust than fossil carbon.

    Per unit of heat created wood produces even more CO2 than the fossil fuels do.

    How so? The exothermic reaction of oxygen and carbon atoms produces a calculable output of heat per CO2 molecule and CO2 production is per atom of carbon?
    CO2 from wood is also recycled atmospheric CO2, rather than an overall increase added to the atmosphere from fossil sources.

    Furthermore, the black carbon particulate matter released enhances the absorption of radiant heat in the atmosphere, making global warming worse,

    That would be local atmospheric warming from intercepted sunlight, (reducing local surface warming below it, by reduced light reaching the surface) rather than global warming.
    Also, where particulates seed cloud formation, that increases albedo from cloud tops, reflecting sunlight back into space, hence reducing local surface and lower atmospheric temperatures.

    Wood burning by humans is a tiny CO2 input to the atmosphere, when compared to the global billions of tons of fossil fuel burned annually, and the massive feed-back effects of peat and forest wild-fires.

    and prematurely melts already imperiled mountain snow pack.

    That would be so where the smoke interacts locally with snow clouds over mountains, or darkens the surface of lying snow, but most particulates are washed out of the atmosphere by rain.



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  • Wood burning is highly eco, when it is properly combusted and the heat properly recovered.

    The trick is to have a sufficiently high combustion temperature to manage the chemistry of the flue gas. The energy invested in the latent heat of vapourisation of water and carried away and lost by steam is managed by sufficient heat extraction surface area of the flue before release.

    Burning things is eco when done right.

    Making things out of vegetation and burning them when we’re done is not a bad strategy.



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  • Having recently watched “Merchants of Doubt”, I can’t help but wonder if a lot of the “facts” in Peteys post #16 didn’t come from the tobacco lobby. Utah Physicians for a Healthy Environment. Sounds suspiciously like the kind of lobby group set up to muddy the waters around the harm of tobacco smoking.

    Watch the documentary if you can. Fire retardant furnishings, a tobacco-inspired hazard in its own right. Who’d have thought it? (Target the fuel, not the ignition source. Smoking in bed doesn’t kill you, it’s all that damn flammable soft furnishings that are to blame).



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  • bonnie2 #20
    Sep 10, 2016 at 8:09 am

    uphe.org/priority-issues/

    That does put the wood-burning into context of all the other more major forms of pollution.

    @link – We require emissions testing of all those cars, but not wood burning appliances. Why? The EPA estimates that the lifetime cancer risk from wood stove smoke is 12 times greater than that from an equal volume of secondhand tobacco smoke.

    While smokey low temperature wood stoves are polluting, (- particularly if they burn green or damp wood), – these claims seem to be very vague – with no types of stove mentioned. no distance from the stove pipe indicated, and no density of second-hand tobacco smoke indicated.



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  • On returning to their camps, they would divide the meat, and retire to their individual domiciles for the food to be cooked and eaten.

    This statement from comment 10 has stuck in my craw since the minute I read it. A quick internet search at the time produced nothing of interest. Now I want to investigate this claim more deeply. My town library has been closed for a month for renovations, crippling my ability to access books on impulse. When it opens in a few weeks this will be my first binge reading topic. The library is across the street from my house. I grab all books on a given topic that are in house there and request any additional books to be shipped in from other locations if they have supplementary material.

    On October 8 the Peabody Museum of Archaeology and Ethnology at Harvard U. is having their 150 year anniversary open house party. The staff will be on hand and I won’t miss this opportunity to get in there and pick their brains! They have a wonderful collection of native American artifacts and I want to hear their opinion on this smoke-fire-human evolution topic. Did they hunt and gather in groups but then come back to campsite and divvy up the take by nuclear family groups? Did they then cook their meals in separate nuclear family groups?

    As I stated above, this seems to be the least efficient way of cooking for a large extended family I can think of. Anthropology has been guilty of severe bias in the past and I want this question to be reexamined. If it turns out that nuclear family paradigm was foisted on native Americans then we need to correct it for the record. If it turns out that the hunting and gathering was done in groups but then food was divided and cooked by nuclear family groups then so be it.

    I remain skeptical.



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  • OHooligan #19
    Sep 10, 2016 at 7:31 am

    Having recently watched “Merchants of Doubt”, I can’t help but wonder if a lot of the “facts” in Peteys post #16 didn’t come from the tobacco lobby. Utah Physicians for a Healthy Environment. Sounds suspiciously like the kind of lobby group set up to muddy the waters around the harm of tobacco smoking.

    The link to Utah Physicians for a Healthy Environment from Bonnie @#20, gives a more balanced view of pollution sources than #16, so that list may not have been a direct quote from their site, but looks more like a revamped cherry-picked version of selected bits which Petey may have found somewhere else.



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  • I have crawled through countless lofts in London throughout the forty years I worked as an electrician. Before health and safety, I was never given a mask. The soot in most lofts closer to the centre of town, would be mixed with larger dust and fill the spaces between the joists. It would be piled up in the corners and the slightest movement would cause the soot to fly. More if I had to crawl about on my belly. I frequently got nose bleeds but no one pulled this up and made me wear a mask as a young man more worried about image. This soot is another suspect for my lung condition. There must be a huge amount in the many lofts of London being blown about and out of these lofts. Will take some cleanup.

    On a much larger scale!

    http://www.dailymail.co.uk/sciencetech/article-3686504/Did-dinosaurs-smoke-Mass-extinction-reptiles-caused-SOOT-following-asteroid-impact.html



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  • I find it incredibly sad that a former healthcare professional whose specialty was cardio-pulmonary disorders would not be aware of the abundant research about the health effects of wood smoke, including, and most especially, its cardio-pulmonary health effects. Wood smoke doesn’t have nicotine, but nicotine isn’t the most harmful component of cigarette smoke. It’s the fine particulate matter, along with the polycyclic aromatic hydrocarbons such as benzo(a)pyrene (the first carcinogenic compound to be discovered), and other chemicals and compounds such as benzene and formaldehyde that are the most damaging components of cigarette smoke. These are also in wood smoke, only in much, much greater quantities.

    A recent research review found that there is no reason to assume that the particulates in wood smoke are any less harmful than those from other sources, and other studies have shown they are even more harmful. There are far too many research papers on the harms of wood smoke and particulate pollution to add them all here, so I’ll simply post links to a couple of review studies below.

    I’d also like to add that the thought of Utah Physicians for a Healthy Environment being a front for tobacco companies is pretty funny. I personally know one of their board members. They are indeed real doctors in Utah, and their only motivation is a deep belief that everyone should be entitled to clean air and a healthy environment.

    “The sentiment that woodsmoke, being a natural substance, must be benign to humans is still sometimes heard. It is now well established, however, that wood-burning stoves and fireplaces as well as wildland and agricultural fires emit significant quantities of known health-damaging pollutants, including several carcinogenic compounds (e.g., polycyclic aromatic hydrocarbons, benzene, aldehydes, respirable particulate matter, carbon monoxide [CO], nitrogen oxides [NOx], and other free radicals…” ) http://www.vtwoodsmoke.org/pdf/Woodsmoke-health.pdf

    “In comparison with the present general estimations for ambient particulate matter and adverse health effects, the relative risks were even stronger in the studies in which residential wood combustion was considered a major source of particulate matter. Thus there seems to be no reason to assume that the effects of particulate matter in areas polluted by wood smoke are weaker than elsewhere.” http://www.sjweh.fi/show_abstract.php?abstract_id=729

    The California-based Families for Clean Air also has a website about wood smoke:
    http://www.familiesforcleanair.org

    Utah Physicians for a Healthy Environment also have a report about wood smoke: http://uphe.org/priority-issues/wood-burning/uphe-report-on-wood-burning-2015/



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