"Pollution" Prevents Asthma

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Many political environmentalist groups such Florida PIRG artfully hint that increasing asthma rates are tied to air pollution. One problem–for the past 3 decades air pollution has been declining in the United States even as asthma rates climbed. It is true that air pollutants can and do trigger asthma attacks, but there is very little evidence that air pollution causes someone to become asthmatic.

Instead, as I pointed out five years ago, research is pointing increasingly to the "hygiene hypothesis," that is, a too clean environment is responsible for the jump in asthma and allergy rates. Now USA Today is catching up and reports:

Here's the conventional wisdom: Pets promote allergy, kids shouldn't eat peanuts until they're at least 3, and intestinal worms are nothing more than an icky reminder of life before flush toilets.

Here's the new wisdom: Early exposure to pets, peanuts and intestinal worms might actually be good for you, because they program the developing immune system to know the difference between real threats, such as germs, and Aunt Millie's cat.

In other words, exposure to pets, parasitic worms and such like help tune a young child's immune system so that it learns not to overreact to harmless environmental contaminants causing allergies and asthma attacks. In my article I suggested, "Perhaps in the future, doctors will tell parents to administer tapeworms or measles to tune up their infants' immune systems for the long haul." The USA Today article cites researchers who fed Gatorade laced with the eggs of pig whipworms to people with autoimmune Crohn's disease. The result was that the majority of them went into complete remission.

Whole thing here.

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  1. The higher rates of asthma among kids living in crummy rental housing would suggest that the cleanliness of the environment is not the cause of the asthma spike.

    If asthma was concentrated in new homes in the burbs, that would be different.

  2. I read of a study in Germany; there was a school where roughly half the kids lived in modern American-style suburbs, and the other half lived on farms surrounded by animals and dander and dirt. The suburban kids had fairly high rates of asthma and allergies, but among the farm kids such problems were almost nonexistant.

  3. Not to say there’s isn’t somehting about urban areas and asthma in children, but some of the “spike” is due to changes in the mid 90s in how asthma is diagnosed.

    I’m also betting the fact that pulmonolgoy was thought to be a growing field in medical schools in the 80s leads to increased awareness of asthma.

    Here’s a prediction: Since many docs now in school are going into endorinology now to deal with the diabetes “epidemic”, be prepared for an increase in endocrine related disorders in the next 10 years.

  4. My pediatrician suggested that going to day care as an infant can prevent or reduce allergies and asthma, because the other cute little vectors of infection provide germs and ickiness that the livestock did in the past. It was her opinion that getting a few minor respiratory infections as an infant calibrated the immune system, and that missing those small insults meant both a greater chance of nastier illnesses as well as allergies later on.

    My older son had an antibiotic resistant ear infection at six months, got ear tubes, and has been sick exactly twice since then. (He’s seven.) My younger son, however, required six months of antibiotics for a non-contagious condition as an infant, meaning he never got the ear infections as a baby, and he developed fairly bad allergies. (No asthma, thank goodness, though, and he was completely cured of the other problem.) Our experience doesn’t prove anything, but I do find it significant that the kid who got the respiratory infections has a steel immune system and the one who didn’t gets a runny nose any time something blooms in the central time zone.

  5. I don’t remember anyone being allergic to peanuts when I was a kid. I hear about schoolkids having bad reactions to peanuts every year at the school closest to my house. Is it like that everywhere now?

  6. Do you have a cite for the rates of asthmatic children in cities v. suburbs, joe? I don’t feel like combing the entire CDC site. (And I’m dubious that “crummy rental housing” = “cities,” and that the former doesn’t exist in the suburbs.)

  7. I know anecdotal evidence isnt worth beans, but as a lifelong allergy sufferer Im going to weigh in anyway. some facts:

    Recieved allergy shots as a kid; ragweed, pollen, mold.

    No food allergies.

    Had pets as a young kid, briefly as many as four cats and three dogs at 8 years old.

    Developed severe cat allergies in my teens after not having a cat for several years. To this day nothing sets of my asthma worse than being with a cat for half an hour or so.

    My other allergies, ragweed, pollen, etc (but not cat), lessened, though did not disappear, as I improved my diet and, in particularly, quit drinking milk. Or maybe thats coincidence. But Ive kept it up.

    I traveled to Moscow in college, now thats some fucking air pollution. Only time, even in L.A., that nasty outside air gave me asthma fits just sitting down. Usually Id have to try and run a few miles in hazy humid D.C. midsummer air during five oclock rush hour to get that kind of effect.

  8. Do you have a cite for the rates of asthmatic children in cities v. suburbs, joe?

    Probably from reading too many scare articles in Mother Jones. I was particularly fond of this one, which included a discussion linking asthma to Global Warming.

  9. It may very well be that air pollution prevents asthma. However, such a statement is meaningless without qualifiers on what types of pollutants you’re referring to. Reducing sulfur dioxide and NOx emissions probably won’t have the same effect on asthma as, say, particulates. And not all particulates are created equal with regard to asthma. Size and composition matter greatly.

    So you can’t just say “Look, clean air!” without saying what type of pollutants you’re referring to. Well, you can say it, but you can’t really draw any useful conclusions. You didn’t refer us to any specific measure of air quality, you just linked to an EPA web site that in turn offers several reports. Could you tell us which aspect of air quality you are referring to?

    Not to mention that as kids spend more time indoors you need to look at their indoor environments.

    Basically, I don’t see what conclusions you can draw from non-specific statements about outdoor air quality and a trend concerning asthma. Oh, no doubt our favorite lawyer could pick something out of thin air and say that there MUST be a connection, and anybody who doesn’t see it is on the take. But I expect better from a science correspondent.

  10. Like Jennifer, I saw a report of a German study that did environmental bacterial/fungal cultures + periodic health checks of all under 18 children over the course of 2 years in both urban, suburban, and farm households several years ago, looking for correlations between the enviromental vectors and childhood alergy/asthma occurances. The initial findings stated in what I saw trended towards the “dirty farme kids have less long term problems with alergy/asthma conditions. Sorry I can’t attribute this report.

  11. I wonder if there could also be a connection between “natural” and “unnatural” pollution? For example, we all evolved to be surrounded by pollen and animal dander, so a young kid needs to be exposed to these things in order to avoid developing allergies to them. But there are quite a few modern pollutants that we did NOT evolve to handle, and could presumably wreak havoc with immune systems.

    So maybe Ron Bailey and Joe are both right, to an extent–kids exposed to dirt and animals and bug eggs in their youth will be healthier than kids raised in squeaky-clean suburbia, but at the same times kids exposed to various nasty pollutant chemicals will be less healthy than their cleaner counterparts.

  12. We may want to consider the London Fog (in the 1950s). People did not connect pollution with the death rate until spikes in pollution coincided with spikes in the death rate. Apparently air pollution had killed many people off all along.

    As an alternate working hypothesis, we could assume that air pollution disproportionately killed those with respiratory problems including asthma and certain allergies; declining air pollution meant increasing survival chances. People who might have died from severe childhood asthma + severe air pollution now survive.

  13. Dave W., yesterday I went to a talk by a very good biologist doing very important work on cancer, but it seemed to me that she was making some huge (and questionable) assumptions that my computer models will be able to test. A computer and a salary for one physicist is cheaper than the several people and vast amount of equipment needed to do the experiments with the questionable assumptions.

    My work isn’t about creating one more academically interesting paper. It’s about finding cheap ways to put assumptions to the test, so people using expensive equipment don’t chase down quite as many blind alleys. And that type of endeavor is useful whether the disease at hand is cancer, diabetes, asthma, or whatever.

  14. I am not saying your work is useless, T. I am just saying that it is not as important for society as getting a quick grip on how strongly various substances are correlated with diabetes and asthma.

  15. The problem with what you say is that low income urban kids are going to have higher exposure to dust mites/particulates/animal dander/mold spores

    Not necessarily. I live in what is technically a low-income urban area, and apparently every building in my neighborhood has a “no pets” rule. I don’t know about mold and dust, but at least as far as animal dander is concerned, I wouldn’t be surprised to find kids here who have never been exposed to an animal in their life. Not a lot of green stuff in the area, either. So in my neighborhood, I’d say that “unnatural” pollution is probably fairly common, but “natural” pollution is rare.

  16. George Carlin did a routine similar to this (“Fear of Germs,” I think) that made a lot of sense. The routine basically said that if kids don’t play in the dirt and eat some germs now and then, the body never learns how to fight them.

  17. joe: My usual apparently fruitless plea to you–please read the links.

    thoreau: Same plea this time too. The EPA link was to a number of articles, press releases which you could click on to find the data–I would have linked directly to one or other of them, but somehow the EPA would not let me copy their report URLs so that I could pick one. If you had had time to click and read you would have found that all 6 criterion air pollutants emissions are down over the past 30 years, some of them by more than 50%.

    Jennifer: You’re right about the German study

  18. Ron-

    OK, I looked at one article. It seems clear that particulate emissions from industrial sources are declining. Fair enough. I doubt that the other pollutants listed in the report have much to do with autoimmune diseases, but I could be wrong on that.

    I think Jennifer raises a plausible point: We’re no longer exposed to the things that we evolved to be exposed to, so our immune systems can’t learn the way that they evolved to learn. I don’t know if it’s true, but it’s plausible to consider. One could even hypothesize that, in the absence of the stimulants that we’re used to, we react to industrial emissions, even declining levels of emissions, because there’s nothing else to react to. I don’t know if that’s right, but it’s plausible to consider and test.

    So, one could hypothesize that air pollution, even at today’s lower levels, does in fact cause asthma, because the body lacks the stimuli that would normally condition the immune system to resist the onset of asthma.

    It will be interesting to see more data in the coming years.

  19. Read the links, Ron. The rural vs. non-rural distinction is fleshed out, but the complicating distinction I was talking about isn’t. That’s why I raised it. If “living in cities and suburbs,” away from farms, was all or most of the answer, we’d expect urban and suburban communities to have similar rates of asthma. They don’t.

  20. The kids in urban neighborhoods have the worst of both worlds, so far as Ron’s and Joe’s points are concerned–little to no exposure to natural things like pollen and dander, but heightened exposure to chemical pollutants we never evolved to handle.

  21. It is purely anecdata, but the number of children with any sort of allergies was very small when I was growing up compared to my own children’s cohort, and I think the hygene hypothesis makes perfect sense.

    Then, again, allergies were something of a luxury good when I was a child and someone had to be seriously allergic before medical attention was sought, so I suspect we are finding more allergies because we are looking for them more often.

    And finally I further suspect that we are simply breeding weaker stock as the medical state of the art permits more sickly infants to survive, etc. For example, though I have no evidence to support this, I strongly suspect that the incident of myopia is much higher in the general population than it was centuries ago. Thus, perhaps both nurture *and* nature are afoot here.

  22. D. A. Ridgely-

    Your point about searching for allergies is a good one.

    As for myopia, the risk of coming down with it seems to increase greatly if you do a lot of reading or any other work that requires you to spend long periods of time focusing on nearby objects rather than distant objects. So I think changes in lifestyle can explain that one.

  23. joe: Do you think that people are exposed to more cockroach detritus nowadays than in the past? That doesn’t seem plausible. More plausibly is that the immune systems of people which once would have not become sensitized to cockroach feces because they had been tuned in early childhood by parasitic worms, upper respiratory diseases, and exposure to endotoxin (essentially bacterial shells shed by animals) are now overreacting. Once someone becomes asthmatic (overreactive to relatively harmless stimuli) then all kinds of insults can set it off including air pollution.

    Thoreau: As you will no doubt note, the above scenario could work for air pollutants as well. The question is how to balance immune system overreactions with air quality.

  24. We’re no longer exposed to the things that we evolved to be exposed to, so our immune systems can’t learn the way that they evolved to learn.

    This… stuff you breathe, this stuff you live in… the shields of artificial atmosphere we have layered about every planet… the programs in those computers that run your ship, and your lives, for you — they bred what my body carries! That’s what your science has done to me; you’ve infected me… Only the primitives can cleanse me; I cannot purge myself until I am among them. Only their way of living is right — I must go to them.

  25. The kids in urban neighborhoods have the worst of both worlds, so far as Ron’s and Joe’s points are concerned–little to no exposure to natural things like pollen and dander, but heightened exposure to chemical pollutants we never evolved to handle.

    Just quibbling here, but most of the pollutants that are considered important by the EPA (SO2, NOx, CO, particulates, ozone) come from natural sources as well.

    In fact, considering humanity’s close coevolution with fire, maybe kids aren’t getting enough carbon monoxide and fine particulates anymore and that’s what’s causing the asthma.

    Not a problem with me, BTW. I’ve always thought that sitting outdoors around a campfire and breathing in the smoke was healthy.

  26. Just quibbling here, but most of the pollutants that are considered important by the EPA (SO2, NOx, CO, particulates, ozone) come from natural sources as well.

    True, but the amounts are much higher from unnatural sources. The occasional whiff of ozone after a nearby lightning strike will have almost no effect on you, whereas breathing in ozone almost constantly certainly will.

    I’m just saying that I think both Ron and Joe are right–it’s probably not good for a kid to be raised in an unnaturally sterile and clean environment, and also probably not good for a kid to be raised in an area that’s heavily polluted.

  27. For those of you looking for actual data, here are a couple sources:

    http://ajrccm.atsjournals.org/cgi/content/full/164/10/1829

    and

    Braun-Fahrlander C, Eder W, Schreuer M, Riedler J, Carr D, Maisch S, Waser M, Schierl R, Nowak D, von Mutius E. Exposure to farming environment during the first year of life protects against the development of asthma and allergy. Am J Respir Crit Care Med. 2001;163:A157.

    Found by searching Google for: germany allergies city farm

  28. Ron,

    I don’t believe that there is higher exposure to insect droppings now that in the past. But please note, my point about the insect droppings was not to make a comparison over time, but across geography. There is certainly higher exposure to insect droppings among the urban poor than the suburban middle class.

    But wouldn’t many of the “insults” that kids in cities are more exposed to also count as the “tuning up agents?”

    I suppose it is possible that exposure to “tuning up agents” could have decreased over the past 30 years, while exposure to “insults” remained steady, but it seems unlikely. Kids still get colds all the time, and germs and endotoxins would seem to go hand in hand with the presence of the “insults.”

  29. For those of you looking for actual data,

    I think you’re knocking on the wrong door, Mr. W.

  30. For those of you looking for actual data…

    Yep, I’m a virtual data guy, personally.

  31. In all seriousness, although this research might provide some interesting conversation, I’d still need to see many more studies showing the same results before I start giving Trichuris eggs to my kids.

    There are many different possible causes of asthma, and I doubt any one of them will provide a “magic bullet” for asthma sufferers.

    Indeed, increases in asthma rates might simply be evolution in action. In the past 100 years, there has been an unprecedented revolution in medical care. Children that would have died from childhood infections during the 1800’s instead survived to have their own children during the 1900’s.

    What we are seeing today in high asthma rates might be the result of asthmatic children — who by the very nature of their condition are much more vulnerable to respiratory infections — surviving and passing their genes on to the next generation. And as their children and grandchildren and great-grandchildren increase in number, so does the frequency of asthma in the population.

  32. For example, though I have no evidence to support this, I strongly suspect that the incident of myopia is much higher in the general population than it was centuries ago.

    I doubt that that has anything to do with evolutionary pressure. It’s more likely a change in environment rather than heredity. If you’re a medieval farmer, so what if you can’t see things far away? You don’t need to be able to see all that well; you’re almost certainly illiterate anyways. You don’t need good vision to work a plow, or hoe a field, or work a scythe. There wouldn’t, I think, be any evolutionary pressures against myopia in an agrarian society. In a hunter-gatherer society there would be, certainly, but that’s not what you’re saying. I’m guessing that the incidence in myopia increased during the Agricultural Revolution ~10k years ago, and has stayed relatively steady since, with a rise in the last few centuries as people became more literate and did more close-up work with their eyes.

  33. Alright Ron. You can take your boy to the emergency room the next time he gets food poisoning from eating turds or drinking from a pond.

  34. Thoreau I lived 30 years ago in Passadena and it was a clear day I could see Mount Baldy right on top of me. I work now 30 (?) miles south in OC and it’s a smoggy day I can’t see the mountain. The air is just worlds better. Other places with bad air quality back in the day like Pittsburg and Chicago are similar. Mostly what’s gone is stuff you can’t see through and stuff that stings your eyes.

    The inceases in asthma and childhood obesity certainly can’t be slowed by the “stranger danger” panic. Now that kids can’t play outside on their own anymore, they are getting much less light exercise than earlier batches.

    Joe this would be more of a problem for urban kids since they are less likely to have soccer moms.

  35. You know how sometimes movies or television shows will use the plot device of showing the same thing from different angles? On the off chance that anybody wants to do the same thing with this thread, here’s my point of view:

    RON: It looks like being raised in a somewhat natural environment (in terms of allergens like pollen) might be healthier than being raised in a sterile environment.

    JOE: No, because being raised in a down and dirty inner city is more unhealthy.

    ME: Well, you’re dealing with different pollutants in both cases. Sounds like they’re both right.

    RON: Yes, Joe, but kids raised on farms tend to be healthier than kids raised in the burbs.

    JOE: But that ignores all the urban kids who get sick.

    ME: You know, I really don’t see how these two contradict each other. Maybe it’s good for kids to be exposed to pollen and bad for them to be exposed to industrial chemicals.

    JOE, or maybe RON: Something about cockroach poop.

    RON, or possibly JOE: Something else about relative amounts of cockroach poop.

    ME: What is this disagreement about anyway? Oh, forget it. I’m off work. Good-night, y’all.

  36. I get blamed for everything.

  37. Let’s keep in mind that exposing several generations to microscopic amounts of small pox in their youth is what rid the most of world of small pox. Small amount of “bad” stuff can be very good for you.

    Once again, the inescapable conclusion is that men should lick more pussy, women should swallow more jizz, and everyone should lick more ass.

  38. Let’s keep in mind that exposing several generations to microscopic amounts of small pox in their youth is what rid the most of world of small pox.

    Well, exposing the previous generations to microscopic amounts of small pox is also what caused so many smallpox deaths. 🙂

  39. A couple years ago or so I discussed with Ronald Hoffman on the radio findings like these. I found it funny (in the ha-ha sense) that the relationship would be as simple-minded that after IgE had been figured to be useful against parasites (such as worms) that someone would try and find that parasites would be good against an excess of IgE! But results speak, huh?

    Also some years ago a low concentration of endotoxin was found to promote wound healing. Another example of the J curve, as in hormesis.

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