12 ChemMatters, OCTOBER 2006 http://chemistry.org/education/chemmatters.html

AirPollution

ComesHome

By Michelle Laliberte

How many times have you been toldthis? You might have thought thiswas just a way to get you out of yourparents’ hair for a while. But there

might be some sound chemical reasons tospend some time outside of the house. That’sbecause air pollution can sometimes be a realproblem—inside the home!

All kinds of activities that take placeinside the home can release chemicals or par-ticles into the air. Some are obvious, such asusing an aerosol deodorant or painting aroom. Some are less obvious, like taking ashower, frying food, or rolling on the newplush carpet with your pet dog. In drafty oldbuildings, this was not a big problem, becausethere was enough ventilation to prevent thesesubstances from building up. But to bringfresh air into a building and heat it in the win-ter or cool it in summer costs money. Inresponse to the energy crisis in the 1970s,builders started sealing up homes and officebuildings and air circulation decreased drasti-

cally. With poorer circulation, chemicalsreleased inside the home could build up topotentially dangerous levels. Now, growingpublic awareness of indoor air pollution hasgiven birth to new terms such as “indoor environmental health” (IEH), and “sick build-ing syndrome” (SBS). But news reports maysometimes go too far, sensationalizing thesubject to the point of scaring the daylightsout of us. Should we be worried? What shouldyou do?

Sources of indoor air pollution

Stanley Watras lived in Boyertown, PAand worked at the Limerick Nuclear PowerPlant. During December of 1984, Stanley setoff alarms at the plant as he attempted toenter through portal radiation monitors. Everyday for two weeks Stanley went throughdecontamination while the authorities at thenuclear power plant tried to find the source ofhis radiation contamination. It was confusingbecause the power plant was not yet produc-ing fission products, but the contaminationsource was eventually found.

It was coming from Stanley’s house. AtStanley’s urging, his home was tested for

radiation contamination, and it showed radonlevels 650 times the average level. Radon is anaturally occurring radioactive gas that is abyproduct of decaying uranium and a knowncause of lung cancer. His family, includingsmall children, was immediately evacuated.High radon levels were also found in nearbyhouses. Stanley’s home is on the ReadingProng, a region that stretches from Reading,Pennsylvania through New Jersey and intoNew York. This granite formation has veryhigh deposits of low-grade uranium.

RadonRadon-222 is produced by the natural

disintegration of the radioactive elementradium-226. Radium itself is produced by thedecay of uranium-238, which is found in rocklayers and bedrock. It is present in most ofthe soil and rock around the world, especiallyareas with lots of granite, shale, and phos-phate rock.

With the loss of an alpha particle, radiumis converted to radon gas. Radon itself is notharmful. It is chemically inert (it’s a noble gasafter all) and has a short half-life of only 3.8days. However, Rn-222 undergoes radioactivedecay to form polonium-218, which in turnundergoes decay in a continuing chain termi-

“Why don’t you goplay outside and getsome fresh air?”

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nating in stable Pb-206. These progeny nucleiare charged and chemically reactive, so theyattach to airborne dust particles that can beinhaled into the lung. Several of the progenyare alpha-emitters; when they undergo decay,the energetic alpha particles blast into anddamage the surrounding cells.

Because radon is a gas, it can permeateyour house through the basement or crawlspace or through exposed soil and rockbeneath and around your home’s foundation.Sometimes, it can seep in through well water,or migrate into your home through naturalgas lines.

In order to measure and report anamount of radiation, we need a standard unit;the standard measure for the intensity ofradioactivity of some radioactive substancesis the curie (Ci). The curie is a measure of thenumber of atoms in a collection of atoms thatare giving off radiation per an interval of time.Radium decay is used as the basis for thecurie, and one gram of Ra-226 gives off 2.2trillion decays per minute. A curie is a lot ofradiation, so we routinely speak of radiationintensity in terms of a picocurie. Pico is a prefix meaning one trillionth, or 10-12, so apicocurie (pCi) is equal to 2.2 disintegrationsper minute.

Back to radon—the EPA has set safelimits for indoor radon at 4 picocuries perliter of air (4 pCi/L). The average indoor levelof Ra is 1.3 pCi/L, and about 0.4 pCi/L is nor-mally found in air outdoors. The level ofradon gas in Stanley’s (remember Stanley?)home was an astonishing 415 pCi/L, a levelthat has been estimated to carry a risk equiv-alent to smoking 135 packs of cigarettes perday. In fact, this level of radon far exceedsthat allowed in uranium mines!

Radon gas problems can be corrected(mitigated) by increasing ventilation through-out the house, especially in the basement.Sealing cracks and openings in the foundationcan also help to keep some of the radon out.You can't smell it, so to be safe, all homesshould be tested for radon gas levels; com-mercial test kits are available at many hard-ware stores. So, what happened to StanleyWatras? He and his family eventually movedback into the home after fixing the radon

problem, and now Stanley is successfullyworking in the radon mitigation field!

FormaldehydeFormaldehyde (CH2O) is a volatile and

flammable organic chemical that can bereleased into the air as a pungent, suffocatinggas. It is naturally produced in our bodies invery minute quantities as part of normalmetabolism. We are exposed to formaldehydein the air, food, and in cosmetic products.Known by its other names methanal, methyl-ene oxide, and formalin (a 37% mixture inwater), formaldehyde is one of the top 25most abundantly produced chemicals in theworld. It is used as a disinfectant, preserva-tive, fire retardant in foam insulation, clothing,paper products, carpeting, and—yuck—embalming fluid. Formaldehyde is added tocotton products to givethem wrinkle-resistance,and is added to manymore products, including(believe it or not) Italiancheeses, fish, driedfoods, and toothpaste.

When combinedwith urea or phenol,formaldehyde makes anexcellent adhesive resin,so it is widely used in thebuilding and furnishingsindustry. The construc-tion of pressed-woodproducts such as parti-cleboard often involvesthe use of formaldehyde-based resins. You can

find particleboard all through a home as subflooring and shelving. The formaldehydereacts chemically with urea or phenol to forma resin that binds the materials of particle-board together. Formaldehyde reacts withphenol to form 2,4-dimethylol phenol (A).This compound reacts with 2-methylol phenol(B) in a condensation reaction to form com-pound C. A condensation reaction is onewhere two reactants are joined together as asmall molecule is split out; in this case, thesmall molecule is H2O. Compound C poly-merizes to form the resin known as Bakelite,which sets, or hardens, binding particlestogether.

When the polymer resin forms and thematerial sets, there is not supposed to be anyformaldehyde left; it should have all reacted.The problem comes from small amounts ofunreacted formaldehyde that gets entrappedin the resin and is released over time. Therelease, or outgassing, of the excessformaldehyde is gradual, occurring rapidly atfirst and then slowing over time. Thus, expo-sure is greater in a new home furnished withnew products.

Formaldehyde is a potent eye, upper respiratory and skin irritant. Exposure causescentral nervous system problems, includingheadaches, fatigue, and respiratory depres-sion. It has the potential for inducing asth-matic attacks and recent epidemiologicalstudies of work-exposed individuals suggestthat formaldehyde causes nasal cancer. Tominimize your exposure, buy solid wood furniture when possible, and keep your homeproperly ventilated.

ChemMatters, OCTOBER 2006 13

238U ! 226Ra ! 222Rn92 88 86

Uranium-238 Radium-226 Radon-222

Several decaysteps

Loss of alphaparticle

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Test kits for radon and CO are commerciallyavailable.

OH

CH2OH

CH2OH

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CH2OH

CH2OH

CH2OH

CH2OH

CH2OH

OH

OHOH

H+

-H2O CH2

+ 2

OH

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CH2CH2

CH2 CH2

H2C

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B C

phenol formaldehyde2,4-dimethylol phenol

The formation of a polymer resin used for particleboard. Formaldehyde is akey reagent.

Molds and biologicalpollutants

Molds, mildew, fungi, bacteria and housedust are some of the main biological pollu-tants in the home. Spores generated frommold and mildew are released into the air andform new colonies wherever they land. Areasof the home with high humidity, such as bath-rooms, kitchens, laundry rooms, and base-ments are sources for these living pollutants.Mold can be found growing on paper, textiles,grease, dirt, and even soap scum.

Rather than a single substance, housedust is a varied mixture of potentially aller-genic materials. It may contain fibers from different types of fabrics; cotton lint, feathers,and other padding materials; dander fromcats, dogs, and other animals; bacteria; foodparticles; bits of plants and insects; and otherallergens peculiar to an individual home.

House dust also contains microscopicdust mites. Dust mites feed off of human deadskin cells. They live in bedding, upholstered

furniture, and carpets;thriving in summer andthen dying off in winter.The Mayo Clinic estimatesthe average bed containsbetween 100,000 and 10million dust mites. You maybe sharing your bed with mil-lions of them! The particles seenfloating about in a shaft of sunlight includedead dust mites and their waste products.Dust mites have been identified as the singlemost important trigger for asthma attacks.Asthma, a chronic ailment that afflicts millionsaround the world, causes inflammation of theairways and affects the way air enters andleaves the lungs, thereby disrupting breathing.

You can pinpoint these triggers of indoorallergens in your home by visual detection.

Keeping mold growth under control is accom-plished by making sure basements, bath-rooms, and other rooms are clean and dry.Chlorine bleach will remove any visual moldand can be used to clean out humidifiers andair-conditioning condensing units. Use vacu-ums with high-efficiency filters and considerreplacing old carpet with hard surface flooringif anyone in your home is sensitive to theseallergens. Wash sheets, pillowcases, and blan-kets weekly. This removes dust mites’ primarysource of food—your dead skin cells.

Carbon monoxideAccording to the Journal of the American

Medical Association, 1,500 Americans dieeach year from accidental exposure to CO, andover 2,000 from intentional exposure (sui-cide). Carbon monoxide is an extremely haz-ardous gas that has no warning taste or odor.It is produced by incomplete combustion oforganic fuels such as wood, gasoline, naturalgas, coal, charcoal, and fuel oil. Like oxygen,carbon monoxide binds to the iron atoms ofthe hemoglobin (Hb) protein molecules foundin our red blood cells, forming a complexcalled carboxyhemoglobin. Carbon monoxidebinds to hemoglobin about 200 times morestrongly than does oxygen. It was longbelieved that because carboxyhemoglobin isunable to transport oxygen, fatal carbonmonoxide poisoning is due to asphyxiation.This sounds bad enough, but a detailed exam-ination of carbon monoxide poisoning revealsa more complicated, more insidious situation.

Hemoglobin is a tetramer, that is, eachhemoglobin protein has the ability to

bind to four oxygen molecules. Itsoxygen binding exhibits a phe-nomenon called cooperativity:once the first oxygen moleculebinds, the protein changes itsshape in such a way that the

remaining three sites bind oxygenmore tightly. This is physiologically

important, making Hb better at bindingO2 in the oxygen-rich lungs and better atreleasing O2 in the oxygen-poor muscles.However, the CO-bonded iron looks (as far asthe protein is concerned) a lot like the O2-bonded iron. So the Hb shifts into high-affinitymode when even one CO is bound per proteinmolecule. This means that it picks up the O2

well in the lungs but cannot release it in the tissues! A person suffering from exposure tocarbon monoxide actually has high oxygenblood content. It’s just that the oxygen cannot

be released where it is needed: the brain,heart, and skeletal muscle. For more informa-tion on this topic, see Tim Graham’s article“The Silent Killer” in the February 2005 issueof ChemMatters.

Carbon monoxide buildup occurs whenflues or chimneys become blocked andexhaust cannot be vented outside. Faulty fur-naces, fuel-burning space heaters, ovens,ranges, and even grills operated in the homewithout adequate ventilation will also causecarbon monoxide buildup. To prevent thisexposure, carbon monoxide alarms and detec-tors are available in stores and should beinstalled to alert you of dangerous levels. Alsomake sure you have your combustion heatingsystems and chimneys checked by trainedprofessionals every year.

Safe havenEven though we have only listed several

of the many toxic indoor air contaminants, thesubject can be frightening. Our homes shouldbe a safe haven, not a hazardous waste dump.Every time you get dizzy, have a sore throat,or have itching, burning eyes will you wonderif it has to do with the air quality of the room?Education is the key to keeping your indoor airclean and healthy. Remember, it’s not just theoutside air we have to be concerned with any-more. A little forethought and action can go along way in preventing major health problemsarising from contamination occurring in yourown home.

Michelle Laliberte is a science writer living inMedina, OH. This is her first article forChemMatters.

14 ChemMatters, OCTOBER 2006 http://chemistry.org/education/chemmatters.html

Dude—do you have any idea what’scrawling all over your pillow?

A barbeque grill is an example of a CO-producingdevice. Never use a grill indoors.

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