This week’s question comes from Amy, who asks “I am a swim instructor and I’m curious what the long term effects of pool chlorine are.”
Well Amy, this is a very interesting question that I am sure most people who use pools regularly don’t consider. Before I get into the known effects, let’s first go over what chemicals they use.
Pools, as most people know, are most often sanitized by chemicals that contain chlorine. The unique, familiar smell of a pool in the summer comes directly from this and chloramines, products of a reaction between the chlorine and some organic molecules. But most people outside of the pool maintenance industry (or a particularly active do-it-yourself-er) aren’t aware of the variety of chemicals used to keep the pool clean and sanitary.
As far as I can find, most pools are sanitized by one of three salts: trichlor (sodium trichloroisocyanurate), dichlor (sodium dichloroisocyanurate), and cal-hypo (calcium hypochlorite). These salts are all used effectively as carriers for chlorine. Trichlor and dichlor react with water to release chlorine (Cl2) and cyanuric acid, which is the base chemical from which trichlor and dichlor are made. The cyanuric acid produced by this breakdown also protects the free chlorine from UV breakdown from sun exposure by weakly bonding to it. Unfortunately, this process also reduces the chlorine’s effectiveness and thus cyanuric acid levels must be monitored to ensure they don’t get too high. Trichlor and dichlor more slowly dissolve in water and are put in the floating canisters present in many home pools.
Cal-hypo is an older method of chlorination that is still used for both primary chlorination and for “shock” treatments that bring the chlorine levels up to required levels. It is less sophisticated than trichlor and dichlor and has no built in UV protection for the produced chlorine. This compound is used most often to “shock” pools with chlorine when they get too low because dichlor and trichlor dissolve too slowly.
On the whole, it appears that most professionally maintained outdoor pools one would encounter would more likely be primarily chlorinated with trichlor or dichlor. The choice between the three is not particularly important, but the attached sources should give a good idea if you’re interested. Regardless of the choice, chlorine levels in the pool should remain above roughly 1.5-3.0 parts per million (ppm) in order to effectively sanitize. This is approximately the same level as chlorinated drinking water.
Insofar as it relates to health, these chemicals are a mixed bag.
- Cyanuric acid is considered non-toxic, with an LD50 of oral exposure of over 10,000mg/kg. LD50 is the dosage necessary to kill 50% (hence the 50 in LD50) 0f the subjects. Thus it would take over 10g per kg of weight to have a 50-50 chance of killing you; in other words, a standard 165lb (75kg) person would require a direct dose in excess of 750g or over 1.5lb. Longer exposure studies on rats show that it does not accumulate in the body and is effectively eliminated from the body within in a few hours. At the huge tested doses, far beyond the rate of any possible human pool exposure, the only reported complications were from cyanurate crystals forming in the bladder and causing an obstruction. There was no shown increase in cancer risk, birth defects, or organ damage.
- Dichlor and trichlor (collectively tested and referred to as chlorinated isocyanurates), because they release cyanuric acid and chlorine, have effectively the same toxicity profile as cyanuric acid in water. Because the chlorine level is very small relative to the amount of water, skin irritation is the only significantly reported complication of long term exposure. According to a German environmental protection agency study, the margin of exposure rating, which measures the overall toxicity rating regardless of route of exposure, for each is over 8. For reference, triclosan (the anti-bacterial agent in hand soap) is a 9.6, sodium hypochlorite is 0.040, and the toxic fixative (allows for long term storage of organic material, ie. formaldehyde) glutardialdehyde is 0.49. Thus, it is reasonable to conclude these chemicals are theoretically safe even at levels much higher than present in a pool.
- Hypochlorite salts (calcium, sodium, etc. hypochlorite) have a much different toxicity profile and thus present a much more risky exposure. As I mentioned above, the margin of exposure of sodium hypochlorite is over 200 times lower than the chlorinated isocyanurates and over 10 times lower than a toxic fixative. This means that they have a toxic exposure limit across all routes (ingestion, inhalation, and skin) that is much lower than even a toxic fixative. It is most dangerous through skin exposure, as it is corrosive and an irritant in higher concentrations. Luckily, these salts are used in very small amounts in pools, but it stands to reason that long term exposure to these compounds present a greater risk, especially to the skin, than with the chlorinated isocyanurates.
- It is also worth noting that the formation of chloramines by any of these compounds have been thought to contribute to respiratory irritation and asthma in swimmers. However, this effect is normally associated with indoor pools, especially ones with poor ventilation.
In sum, it is clear that the use of chlorinated isocyanurates presents a much safer method of pool sanitation. Experimental evidence of minimal long term toxicity from doses much larger than would ever be found in a pool certainly supports this conclusion. It seems, then, that a properly treated and professionally maintained pool should not present a long term health hazard for those who use it, even those who do every day for multiple hours a day. If any, the greatest known risks are of skin irritation and, in the case of indoor pools, respiratory tract irritation.
Hope this helps, Amy! As always, feel free to submit your questions at the link above.
Till next time, abyssus abyssum invocat
Hello everyone! Sorry for the later than usual post, been a hectic week. This week’s question comes from Erin, who asks “I hear a lot about medical uses for marijuana. What, if any, are the actual, proven medicinal benefits of marijuana?”
As we all know, the battle over medical marijuana, and the broader legalization debate, has been in the headlines for the past few years. Proponents claim it helps with everything from cancer treatment to glaucoma to anxiety. Opponents believe it has little to no medical value and should remain entirely illegal. But, in this debate, the facts are often obscured by people’s emotional opinions and pre-conceived notions. I chose to write this post specifically to bring some of the facts to the forefront.
Before we begin discussing the relative merits, we should first understand how marijuana works. Marijuana is a very complex plant that contains a wide variety of chemicals that act on the human body. Primary among these is tetrahydrocannabinol, or THC, which exerts a significant portion of the plant’s effect when ingested. THC is a type of molecule known as a cannabinoid, which attach to the aptly named cannabinoid receptors found throughout the body. A variety of different cannabinoids are found within marijuana, all with different functions, benefits, and possible side effects. These receptors respond normally to the body’s natural cannabinoids, known as endocannabinoids. We know relatively little about the cannabinoid receptor system. We currently only have two receptors, CB1 and CB2, named and generally understood but studies on mice with those receptors removed still are able to feel the effects of THC to a certain extent. This suggests that there are other, possibly many other, different cannabinoid receptors throughout the body. Further research into the functions of cannabinoid receptors is a key part of understanding the various functions of cannabinoid molecules as well as illuminating wider, as of yet not well understood, elements of human biology.
Cannabinoids, as far as we know, are responsible for a variety of marijuana’s medically desirable qualities. Primarily, these effects center around pain relief and appetite stimulation, though far more uses and anecdotal benefits exist, such as anti-depressant, anti-anxiety, and anti-inflammatory effects. Lets dive into some of these proposed benefits and see if there is any scientific foundation to the widely distributed claims.
- Pain relief: Noyes, et al., published a study in 1975 in the journal Clinical Pharmacology and Theraputics, describing the use of THC versus codeine and aspirin for the treatment of pain. They concluded that THC is effective against mild to moderate pain, but that at the higher effective doses it had significant psychoactive effects. This can limit THC’s use as a regular pain reliever, as it would cause significant impairment while performing said function. In his book “Understanding Marijuana: A New Look at the Scientific Evidence,” Earlywhine examined marijuana’s value in treating a variety of types of pain. He could not firmly establish compelling evidence that marijuana had a strong analgesic (pain killing) effect generally. He did mention evidence supporting pain relief for headaches and cancer, but by different, largely speculative mechanisms not directly related to normal types of pain. It is also thought that certain cannabinoid metabolites (the molecules created once the body processes the ones ingested) can have a stronger analgesic effect, however the specific metabolite and its full analgesic potential still remains unknown. The issue of significant impairment still remains a stumbling block for wide use of cannabinoid-based pain medications. However, anecdotal evidence for its utility in this area is plentiful, and this continues to be one of the main uses of medical marijuana therapy. There are active research efforts to isolate the effective molecule(s) for pharmaceutical use as alternatives to current pain medications.
- Appetite stimulation/anti-nausea: I think it is common knowledge that marijuana use stimulates appetite. Mattes, et al., published in the journal Pharmacology Biochemistry and Behavior that while the appetite stimulation effects are highly variable (with dose, environment, age, and duration of use), on the whole the effects were positive. These were especially important when combined with its proven anti-nausea/anti-emetic (prevents vomiting) properties, which make it very useful for people with debilitating conditions such as cancer and AIDS. These elements of cannabinoids are already being used in pharmaceutical drugs such as Dronabinol and Nabilone.
- Anti-depressant/anti-anxiety: Lemberger published an article in the 1980 edition of Annual Review of Pharmacology and Toxicology detailing a variety of potential uses for marijuana. His conclusion, based on the available evidence, was that it is not clear whether or not marijuana has a true anti-depressant and/or anti-anxiety effect or if it simply causes temporary euphoria that masks the depressive symptoms. Cannabidiol, a cannabinoid in marijuana, specifically has been shown to have some action on serotonin receptors in the brain, as well as a variety of other potential health benefits. So it is possible that marijuana could contain cannabinoids that have action similar to anti-depressants and, likewise, anti-anxiety medication. However, these particular functions are not well-defined and research in this area is not well developed, especially relative to the research done on actual anti-depressant and anti-anxiety medications. As of now, then, the data remain anecdotal.
- Anti-inflammatory: Lemberger also explores the anti-inflammatory properties of THC. He notes that there is some noteworthy anti-inflammatory response, specifically related to the formation of prostaglandins. This is thought to be why marijuana is considered a potential treatment for inflammatory conditions such as glaucoma and asthma. Not much is known in this area, but what is known is promising.
It is pretty clear that marijuana, specifically the cannabinoids it contains, has both anecdotal and scientific basis for medicinal use. While the effects are variable and often undesirable from a pharmacological perspective, it remains that the drugs do have value in this respect.
The negatives associated with marijuana use are also well known, but not particularly well-supported. A study by UCSD in 2003 showed the claims of long term memory loss, cognitive impairment, and addiction have been shown clinically to be mild to negligible. This is hardly the final say on negative effects, but at least on the face of it marijuana does not present a particularly distressing long term risk profile. The short-term side effects, largely known as a “high,” may prevent its wide adoption and use in a variety of contexts but are not known to be harmful over the long term. The negative effects largely lie in the route of administration, specifically the risks associated with smoking.
In short, marijuana demonstrates medicinal value. The issue is, we still don’t know much beyond that. Marijuana and other cannabinoid containing plants should be researched more fully to better understand the full effects, both positive and negative, as well as the potential uses. The research conducted thus far, combined with many years of anecdotal reports, is compelling enough to validate this sort of research.
Hope this helps, Erin! As always, feel free to submit your question at the “Submit Your Question” tab at the top of this page. Thank you, as always, for reading!
Till next time, keep it real.