Indoor Environmental Quality - Chapter 4 potx

Those which, at present, areknown to cause either significant indoor air contamination and/or adversehealth effects include formaldehyde HCHO, acetaldehyde, acrolein, andglutaraldehyde..

chapter four Organic contaminants

A large variety of natural and synthetic organic compounds can be found

in indoor environments These include very volatile organic compounds(VVOCs) which have boiling points ranging from <0°C to 50–100°C, volatileorganic compounds (VOCs) with boiling points ranging from 50–100°C to240–260°C, semivolatile organic compounds (SVOCs) with boiling pointsranging from 240–260°C to 380–400°C, and solid organic compounds (POMs)with boiling points in excess of 380°C In the last case, POMs may be com-ponents of airborne or surface dusts

Organic compounds reported to contaminate indoor environmentsinclude a large variety of aliphatic hydrocarbons, which may be straight,branch-chained, or cyclic (contain single bonds [alkanes] or one or moredouble bonds [alkenes]); aromatic hydrocarbons (contain one or more ben-zene rings); oxygenated hydrocarbons, such as aldehydes, alcohols, ethers,ketones, esters, and acids; and halogenated hydrocarbons (primarily chlorineand fluorine containing) These may be emitted from a number of sourcesincluding building materials and furnishings, consumer products, buildingcleaning and maintenance materials, pest control and disinfection products,humans, office equipment, tobacco smoking, and other combustion sources.Organic compounds which are seen as relatively distinct indoor contam-ination problems include the aldehydes, VOCs/SVOCs which include a largenumber of volatile as well as less volatile compounds, and pesticides andbiocides which are, for the most part, SVOCs

I Aldehydes

Aldehydes belong to a class of compounds called carbonyls Carbonyls,which include aldehydes and ketones, have the functional group

in their chemical structure The carbonyl is in a terminal position in hydes A compound is described as an aldehyde if it has one terminal car-bonyl, a dialdehyde if it has two, and a trialdehyde if it has three carbonyls.Aldehydes include saturated (single bonds) aliphatic, unsaturated (one

alde-or malde-ore double bonds) aliphatic, and aromatic alde-or cyclic compounds rated aliphatic aldehydes include formaldehyde (one carbon), acetalalde-hyde (two carbons), propionaldehyde (three carbons), butryaldehyde (fourcarbons), valeraldehyde, glutaraldehyde, etc As can be seen in Table 4.1,glutaraldehyde is a dialdehyde with carbonyls on both ends of the molecule.Unsaturated aliphatic aldehydes contain a carbon–carbon double bond(Table 4.1) They include acrolein (acryaldehyde), methacrolein, and cro-tonaldehyde Methacrolein is commonly used to produce methyl methacry-late, an eye-irritating ester used as an adhesive in many industrial applica-tions Aromatic aldehydes include compounds such as benzaldehyde andcinnamaldehyde

Satu-Table 4.1 Chemical Structures and Properties of Common Aldehydes

Solubility (g/L)

H–C=O|

CH2

O H C CH CH

CH3

Individual aldehydes differ in their molecular structure, solubility, ical reactivity, and toxicity Only a relative few have industrial and commer-cial applications which may result in significant indoor exposures, are by-products of other processes, or have biological activities that have the poten-tial for posing major public health concerns Those which, at present, areknown to cause either significant indoor air contamination and/or adversehealth effects include formaldehyde (HCHO), acetaldehyde, acrolein, andglutaraldehyde Many aldehydes are potent sensory (mucous membrane)irritants; some are skin sensitizers; and there is limited evidence that severalaldehydes may be human carcinogens.

chem-A Sensory irritation

Because of their solubility in aqueous media and their high chemical activity,aldehydes as a group are potent mucous membrane irritants (affecting eyesand mucous membranes of the upper respiratory tract) This irritation isassociated with maxillary and ophthalmic divisions of trigeminal nerves innasal and other mucosa which respond to chemical/physical stimuli Theseserve as respiratory defense mechanisms through the perception of pain orirritation and reduced contaminant inhalation

Measured decreases in respiratory rates in rats and mice on exposure toirritant chemicals have been used to evaluate the irritation potential of alde-hydes and other substances using a standard mouse bioassay Doses required

to cause a reduction of breathing rates by 50% (RD50) for selected aldehydesare summarized for mouse bioassays in Table 4.2 As can be seen, RD50 valuesrange by more than three orders of magnitude Formaldehyde and the unsat-

Table 4.2 RD 50 Values for Swiss-Webster Mice Exposed

to Aldehydes Chemical RD 50 value (ppmv)

Source: From Steinhagen, W.H and Barrow, C., Toxicol Appl.

Pharmacol., 72, 495, 1982 With permission.

urated aldehydes, acrolein and crotonaldehyde, were the most potent sory irritants; the saturated aldehydes, acetaldehyde and propionaldehyde,were least potent These data, which do not include glutaraldehyde (a potentirritant in rats), indicate that only a few aldehydes have the potential to besignificant mucous membrane irritants at the relatively low concentrationsthat occur in indoor environments, such as residences and nonresidential,nonindustrial buildings Of these HCHO, acrolein, and glutaraldehyde arethe most notable Though a relatively weak sensory irritant, acetaldehyde is

sen-a common contsen-aminsen-ant of both indoor sen-and sen-ambient (outdoor) sen-air

B Formaldehyde

Formaldehyde is molecularly the smallest and simplest aldehyde It isunique because the carbonyl is attached directly to two hydrogen atoms(Table 4.1) Due to its molecular structure, HCHO is highly reactive chemi-cally and photochemically It has good thermal stability relative to othercarbonyls and has the ability to undergo a variety of chemical reactions,which makes it useful in industrial and commercial processes As a conse-quence it is among the top 10 organic chemical feedstocks used in the U.S.Formaldehyde is a colorless, gaseous substance with a strong, pungentodor On condensing, it forms a liquid with a high vapor pressure (boiling

at –19°C) Because of its high reactivity, it rapidly polymerizes with itself toform paraformaldehyde As a consequence, liquid HCHO must be held atlow temperature or mixed with a stabilizer (such as methanol) to pre-vent/minimize polymerization

1 Uses/sources

Formaldehyde is commercially available as paraformaldehyde, which tains varying lengths of polymerized HCHO molecules It is a colorless solidthat slowly decomposes and vaporizes as monomeric HCHO at room tem-perature It has been used in a variety of deodorizing commercial products,such as lavatory and carpet preparations

con-Formaldehyde is also commercially available as formalin, an aqueoussolution that typically contains 37 to 38% HCHO by weight and 6 to 15%methanol Because of HCHO’s volatility, formalin also has a strong, pungentodor In solution it is present as methylene glycol (CH2(OH)2); in concen-trated solutions it is in the form of polyoxymethylene glycol (HO-CH2O)n-H

As a chemical feedstock, HCHO is used in many different chemicalprocesses Of particular significance to indoor environments is its use toproduce urea and phenol–formaldehyde resins (50% of HCHO consumedannually)

Urea–formaldehyde (UF) copolymeric resins are used as wood sives in the manufacture of pressed-wood products such as particle board,medium-density fiber board (MDF) and hardwood plywood, finish coatings(acid-cured), textile treatments (permanent-press finishes), and in the pro-duction of urea–formaldehyde foam insulation (UFFI) Urea–formaldehyde

adhe-wood adhesives are colorless and provide excellent bonding performance.They are, however, somewhat chemically unstable, releasing monomericHCHO on hydrolysis of methylol end groups and, less commonly, methyl-ene bridges Their decomposition is sensitive to product moisture levels aswell as relative humidity Because of resin sensitivity to moisture, UF-bonded wood products are intended only for indoor use Historically UF-based adhesives were formulated with relatively high HCHO to urea ratios(F:U 1.5:1) to enhance performance by ensuring that there was sufficientHCHO present to achieve cross-linking of all primary and secondary aminogroups Because of this excess HCHO associated with the resin, UF-basedwood adhesives emitted significant levels of free HCHO into indoor envi-ronments, particularly in the first months or so in the life of a product.Because of high HCHO emissions, indoor concentrations, and health com-plaints, UF-bonded wood products are presently manufactured with lowF:U ratios (e.g., 1.05:1) and thus emit much less HCHO Though HCHOemissions from UF-bonded wood products are substantially lower thanthose of two decades ago (<10%), they continue to be a significant source

of indoor HCHO concentrations Most emissions are associated with thehydrolytic decomposition of the resin copolymer

Phenol–formaldehyde resins receive significant use as exterior-gradeadhesives in the manufacture of softwood plywood and oriented-strandboard (OSB) products that are widely used in new home construction Phe-nol–formaldehyde (PF)-bonded wood products have historically had lowHCHO emissions compared to UF-bonded wood products Emissions fromthe latter were once 1000 times greater than from PF-bonded products.Formaldehyde is produced in the thermal oxidation of a variety oforganic materials As a consequence, it is found in the emissions of motorvehicles, combustion appliances, wood fires, and tobacco smoke It is alsoproduced in the atmosphere as a consequence of photochemical reactionsand hydrocarbon scavenging processes, and in indoor air as a result ofchemical reactions

2 Exposures

Formaldehyde is omnipresent in both ambient and indoor environments.Ambient concentrations are usually <10 ppbv in urban/suburban loca-tions but may reach peak levels of 50 ppbv or more in urban areas subject

to significant atmospheric photochemistry (e.g., south coast of California).Formaldehyde levels in indoor environments are on average significantlyhigher (order of magnitude or more) in residential, institutional, andcommercial buildings than background ambient levels Concentrationsvary from structure to structure, depending on the nature of sourcespresent and environmental factors which may affect emissions and indoorconcentrations

Historically, the major sources of HCHO emissions have been woodproducts bonded with UF resins, UF-based acid-cured finishes, and in housesretrofit insulated (in the 1970s and early 1980s) with UFFI Formaldehyde

emission rates from a variety of construction materials and consumer ucts available in the early 1980s marketplace are summarized in Table 4.3.Pressed wood products have been the major source of HCHO contam-ination in indoor environments Particle board has been used as underlay-ment in conventional homes; floor decking in manufactured homes; compo-nents of cabinetry, furniture, and a variety of consumer products; and as adecorative wall paneling Because of marketplace changes, it is now littleused as underlayment in conventional houses, and fewer than 50% of newmanufactured homes are constructed with particle board floor decking.Hardwood plywood has been used as a decorative wall covering and as acomponent in cabinets, furniture, and wood doors Medium-density fiberboard has been used in cabinet, furniture, and wood door manufacture Acid-cured finishes, which often contain a mixture of urea and melamine–form-aldehyde resins, are used as finish coatings on exterior wood cabinet com-ponents, fine wood furniture, and hardwood flooring.

prod-Urea–formaldehyde foam insulation or similar products are occasionallyused to retrofit insulate houses in North America and are commonly used

in the United Kingdom Prior to a ban by the Consumer Product SafetyCommission (CPSC) in the U.S (subsequently voided in a federal appealscourt) and a ban by the Canadian government in the early 1980s, UFFI wasapplied in over 500,000 U.S residences and 80,000 in Canada

Formaldehyde concentrations in U.S residences based on data collected

in the late ‘70s to mid ‘80s are summarized in Table 4.4 As indicated ously, significant improvements (reduced emission rates) in UF-bondedwood products have occurred since the mid ‘80s, and there have beenchanges in products used in construction As a consequence, HCHO levels

previ-in buildprevi-ing environments (particularly residences) are significantly lower previ-inhouses built since 1990 than in those constructed previously Formaldehydelevels in new mobile homes are rarely >0.20 ppmv, and are more likely to

be in the range of 0.05 to 0.15 ppmv In other new residential buildings

Table 4.3 Formaldehyde Emissions from Construction Materials,

Furnishings, and Consumer Products Product Emission rate range ( µ g/m 2 /day) Medium-density fiberboard 17,600–55,000

Hardwood plywood paneling 1500–34,000

of Standards, Washington, D.C., 1985.

constructed in the U.S and Canada, concentrations are unlikely to exceed0.10 ppmv, with concentrations <0.05 ppmv the norm In office buildings,HCHO levels are rarely >0.05 ppmv, with concentrations in the range of 0.02

to 0.03 more common

3 Factors affecting formaldehyde levels

Formaldehyde levels in building environments are affected by a number offactors These include the potency of formaldehyde-emitting productspresent, the loading factor (m2/m3), which is described by the surface area(m2) of formaldehyde-emitting materials relative to the volume (m3) of inte-rior spaces, environmental factors, materials/product age, interaction effects,and ventilation conditions

As indicated in Table 4.3, formaldehyde-emitting materials have ically differed in their emission potential These differences have decreasedwith product improvements Medium-density fiber board and acid-curedfinishes have been among the most potent formaldehyde-emitting materials

histor-a Loading factor. Mobile homes have had the highest reported centrations of HCHO This has been the case in good measure because ofthe high loading rate of formaldehyde-emitting wood products In the past,mobile homes were constructed using particle board floor decking, Luanplywood wall covering, and wood cabinets (made from various combina-

con-Table 4.4 Formaldehyde Concentrations in U.S Houses

Measured in the Period 1978–1989

Concentration (ppmv)

Urea-Formaldehyde Foam Insulated Houses

Source: From Godish, T.J., Indoor Air Pollution Control, 1st ed., Lewis

Publishers, Chelsea, MI, 1989 With permission.

tions of particle board, MDF, Luan plywood, and hardwood) As a quence, they had relatively high surface/volume ratios (expressed as m2/m3)

conse-of formaldehyde-emitting wood products

b Temperature and relative humidity. Environmental factors such astemperature and humidity have significant effects on HCHO levels in build-ings where UF-bonded wood products are major HCHO sources The effects

of temperature on indoor HCHO concentrations is exponential, whereas theeffect of relative humidity is linear Combined effects of various temperatureand humidity regimes on HCHO levels in a mobile home can be seen inTable 4.5 Note that the highest combination of temperature and humidity(30°C, 70% RH) resulted in indoor concentrations that were 5 times greaterthan the lowest combination (20°C, 30% RH)

Experimentally derived relationships between HCHO levels and perature and HCHO levels and relative humidity have been used to developequations to “correct” (or more appropriately, standardize) HCHO levelsdetermined under different environmental conditions to temperature andhumidity conditions such as 25°C and 50% RH The Berge equation is widelyused to standardize HCHO concentrations It has the following form:

H = relative humidity at test (%)

HO= standardized relative humidity (%)

Table 4.5 Effect of Temperature and Relative Humidity on Formaldehyde Levels in a Mobile Home Under Controlled Environmental Conditions Temperature

(°C)

Relative humidity (%)

Concentration (ppmv) % maximum value

The Berge equation is a relatively good predictor of HCHO concentration

at standard conditions when measured under a variety of environmentalconditions It has been reported to have a standard error of ±12% within a95% confidence level

c Decrease in formaldehyde levels with time. Formaldehyde levelsdecrease significantly with time A generalized relationship between HCHOlevels and product or home age with time can be seen in Figure 4.1 Rapidreductions of HCHO levels can be seen to occur in the early life of formal-dehyde-contaminated residences or emitting products After an initial rapiddecline, HCHO levels decrease at a much slower rate, with relatively ele-vated levels continuing for years

Several investigators have attempted to model changes in HCHO levelswith time, using exponential model equations as well as statistical analyses.Exponential models that describe the decay of radioactive isotopes as well

as first-order chemical reactions predict a constant half-life Studies of fielddata indicate that HCHO decreases with time are exponential only in part,with half-lives that increase in time Statistical and graphical evaluations ofWisconsin mobile homes tested for HCHO in the early 1980s indicated half-life values of 3, 5, 12, and 72 months

Because HCHO levels depend on a variety of source and environmentalvariables, it is unlikely that a model equation could be developed that wouldreliably predict the decay of HCHO levels under the many source and envi-ronmental conditions that have and continue to exist in North Americanresidences However, double exponential models have been shown to berelatively good predictors of changing HCHO levels with time (see Chapter 9).The decay rate is dependent on emission rates that are affected by tem-perature, relative humidity, and interaction effects between formaldehyde-emitting materials, as well as ventilation rates (increasing temperature,humidity, and ventilation rates increase emission rates and, as a conse-quence, decay rate) Therefore, half-lives would be expected to be shortened

Figure 4.1 Generalized decrease of formaldehyde with time.

(HCHO levels would decline more rapidly) with increasing temperature,relative humidity, and ventilation Interaction effects described below would,

if all other factors were standardized, likely increase the time period requiredfor a 50% reduction in HCHO levels

d Interaction effects. In building environments that contain multipleUF-based emission sources, measured concentrations are typically similar

or are slightly above sources with the highest emission potential present(most potent source) rather than the sum of emissions/emission potentials

of all formaldehyde-emitting sources Such interaction effects are due to avapor pressure phenomenon High vapor concentrations associated withemissions from potent sources suppress emissions from less potent sources

e Ventilation. Ventilation associated with infiltration, opening dows, and mechanical induction can affect indoor concentrations of HCHO

win-as well win-as emission rates Formaldehyde levels decrewin-ase with increwin-asingventilation rates The relationship is not linear because a doubling in theventilation rate is associated with only a 30 to 35% decline in HCHO levels(due to increased emission rates) Natural ventilation associated with infil-tration appears to have a significant effect on HCHO levels Under controlledconditions, HCHO levels reach their maximum values when indoor/outdoortemperature differences are small Lowest HCHO levels in northern climatesare observed during the cold season, especially on cold winter days (Figure4.2) when indoor/outdoor temperature differences are large

f Tobacco smoke. Since HCHO is a by-product of combustion cesses, smokers, as can be expected, are exposed to high HCHO levels (onthe order of 40 to 250 ppmv in a single puff) Formaldehyde emissions fromburning cigarettes are indicated in Table 4.6 Nonsmokers are exposed tosignificantly lower levels from environmental tobacco smoke (ETS) because

pro-of the significant dilution effects that occur Because pro-of interaction effects

Figure 4.2 Relationship between indoor formaldehyde levels and outdoor temperatures.

between ETS, HCHO, and UF-based HCHO, the effect of tobacco smoke onindoor concentrations would be small (because of the modulating effect ofUF-based sources).

4 Health effects

a Mucous membrane irritation and neurotoxic effects. The effects ofHCHO on human health have been extensively investigated in human expo-sure studies and field and epidemiological studies of workplace and resi-dential buildings Major health concerns have included mucous membraneirritation, neurological-type symptoms, potential sensitization, and upperrespiratory system cancers

The ability of HCHO to cause irritation or inflammatory-type symptomsand symptoms of the central nervous system (e.g., headache, fatigue) isknown from controlled animal studies, reports of occupational exposures,field investigations, and epidemiological studies of humans exposed toHCHO in residential environments

Controlled human exposure studies at concentrations in the range ofthose reported in residential environments (≥0.03 ≤1.0 ppmv) have beenshown to cause significant eye and nose irritation among healthy volunteers

in 90-minute exposures compared to unexposed controls In 5-hour humanexposure studies, significant decreases in nasal mucus flow were observed

at 0.25 ppmv in healthy volunteers, with slight to significant discomfort andeye and throat dryness increasing in frequency with HCHO concentrationsabove 0.25 ppmv

Elevated prevalence rates of mucous membrane symptoms, central vous system symptoms (headache, fatigue, sleeplessness), as well as nausea,diarrhea, unnatural thirst, and menstrual irregularities have been reported

ner-in field ner-investigations of HCHO exposures ner-in residential and nonner-industrialworkplaces The author observed significant dose–response relationshipsbetween HCHO levels and symptom severity for 14 symptoms/health prob-lems including eye irritation, dry/sore throat, runny nose, bloody nose, sinusirritation, sinus infection, cough, headache, fatigue, depression, difficultysleeping, nausea, diarrhea, chest and abdominal pain, and rashes for a range

Table 4.6 Aldehydes in Cigarette Smoke

Emission (mg/pk) Aldehyde Mainstream Sidestream ETS a

a Environmental tobacco smoke integrated over 2 hours.

Source: From Leikauf, G.D., in Environmental Toxicants: Human

Exposures and Their Health Effects, Lippmann, M., Ed., Van

Nos-trand Reinhold (John Wiley & Sons), New York, 1992, chap 10.

With permission.

of concentrations with a median value of 0.09 ppmv in a study of mobilehomes and homes with particle board underlayment Studies in Canada andCalifornia indicate significant dose-dependent symptoms associated withHCHO exposure concentrations of <0.10 ppmv.

b Asthma. Asthmatic reactions to HCHO and nary-type symptoms have been reported in field investigations of occupa-tional and residential HCHO exposures These studies suggest that HCHOmay be a pulmonary irritant and may be capable of inducing asthmaticattacks by specific sensitization reactions Controlled bronchial challengestudies (which are the standard for confirming the induction of asthmaticsymptoms on exposure to a substance) of asthmatic patients in the U.S andCanada have been unable to identify any changes in pulmonary function atexposure concentrations of 2 to 3 ppmv Less well-controlled bronchoprovo-cation tests in Europe indicate that formaldehyde-induced pulmonary func-tion changes in exposed workers occur but that such responses are rare.Significantly increased prevalence rates of asthma and chronic bronchitisamong children in homes with HCHO levels in the range of 0.06 to 0.12ppmv (especially in homes with ETS) compared to those less exposed wereobserved in an epidemiological study of HCHO concentrations, respiratorysymptoms, and pulmonary function conducted in Arizona A linear decrease

asthmatic/pulmo-in peak expiratory flow rates with HCHO levels was observed with anestimated decrement of 22% at 0.06 ppmv This study is significant since itapparently shows a strong dose–response relationship between pulmonarysymptoms and HCHO concentrations in the range of ≥0.06 to 0.12 ppmv;levels which are still likely to occur in U.S mobile homes Also notable isthat pulmonary function decrements were observed in both asthmatic andnonasthmatic children

The induction of asthma or asthmatic symptoms may occur as a quence of a specific hypersensitivity reaction or a response to a nonspecificirritant The former suggests that an immunological mechanism is respon-sible Though specific IgE antibodies for HCHO have not been demonstrated,several investigators have shown that some formaldehyde-exposed individ-uals develop antibodies against formaldehyde–human serum albumin con-jugates The clinical significance of these findings has not been established

conse-c Cancer. Formaldehyde has been shown to cause a variety of toxic effects in cell culture and in vitro assays These include DNA-proteincross-links, sister chromatid exchange, mutations, single-strand breaks, andaberrations in chromosomes These results indicate that HCHO is both geno-toxic and mutagenic and is therefore likely to be carcinogenic Several high-concentration, chronic animal exposure studies have demonstrated thatHCHO can cause squamous cell carcinomas in the nasal passages of ratsand mice

geno-A number of epidemiological studies have attempted to evaluate thepotential relationship between HCHO exposure and upper respiratory sys-

tem cancer These studies have not provided conclusive evidence of a causalrelationship Formaldehyde exposures have been reported to be associatedwith slight to moderate increases in risk for cancers of the buccal cavity,nasopharynx, oropharynx, and lung Studies of residents of mobile homeshave shown a significant increase in the risk of nasopharyngeal cancer inindividuals living in mobile homes (at exposure concentrations ≥0.10 ppmv)for more than 10 years (compared to a randomly chosen population) Based

on available evidence, the USEPA, Occupational Safety and Health istration (OSHA), and International Agency for Research on Cancer (IARC)have listed formaldehyde as a Class 2A (suspected human) carcinogen

Admin-C Acetaldehyde

Acetaldehyde is a two-carbon aliphatic aldehyde with a pungent, fruityodor Though it is used in a variety of industrial processes, its presence inambient and indoor air is almost always associated with the combustionoxidation of fuels and products such as tobacco (Table 4.6) It is a majorconstituent of automobile exhaust gases and is the predominant aldehydefound in tobacco smoke

Exposures to acetaldehyde (in indoor environments) are likely to occurfrom the infiltration of ambient air, ETS, combustion by-products fromunvented gas and kerosene appliances, flue gas spillage, leakage from wood-burning appliances, and, in developing countries, unvented by-products ofwood, charcoal, and kerosene cooking fuels

Exposures to acetaldehyde in indoor environments have not been acterized Compared to HCHO, it is a relatively mild irritant of the eye andupper respiratory system It is unlikely to cause irritant symptoms in mostindoor environment situations because of anticipated low exposure concen-trations The exception to this may be cooking fires in developing countries.Acetaldehyde is a proven animal carcinogen and, as such, is a potentialcarcinogen in humans

char-D Acrolein

Acrolein is a three-carbon aldehyde with one double bond It is highlyvolatile and has an unpleasant choking odor It is used in the production of

a number of compounds and products It is released into the environment

as a combustion oxidation product from oils and fats (containing glycerol),wood, tobacco, and automobile/diesel fuels

There are few published reports of acrolein in indoor air In an apparentlyunusual case, the author has observed significant acrolein levels (>0.1 ppm,the OSHA PEL) in school administrative office spaces associated with theapplication of a polyurethane insulation/rubberized roofing material.Acrolein emissions and potential human exposures have been reportedfor tobacco smoke (Table 4.6) They also occur in the ambient and indoorenvironments with open windows, as a result of motor vehicle emissions

and atmospheric photochemistry Acrolein levels, like other aldehydes, peak

at midday (on sunny days) Acrolein is present in wood smoke in significantquantities and, as a consequence, exposures may result from leaking wood-burning appliances and from cooking fires in developing countries

Acrolein is a potent eye irritant causing lacrimation (tearing) at relativelylow exposure concentrations It is widely believed that acrolein exposuresare the primary cause of eye irritation associated with tobacco smoke It mayalso be the major cause of eye irritation associated with wood smoke Thoughacrolein has been reported to be both geno- and cytotoxic, it has not beenshown to be carcinogenic in animal studies, nor has there been any epide-miological link between acrolein exposure and human cancer

E Glutaraldehyde

Glutaraldehyde is a five-carbon dialdehyde It is a liquid with a sharp, fruityodor Compared to the aldehydes described above, it has a low vapor pres-sure (0.20 mm Hg at 20°C) and thus volatilizes slowly

Glutaraldehyde is the active ingredient in disinfectant formulationswidely used in medical and dental practice Significant or incidental expo-sures have been reported among hospital, medical service, dental, veterinary,and funeral service staff Exposure concentrations in hospital environmentshave been reported to range from 0.001 to 0.49 ppmv It has also beenreported to occur in some carbonless copy papers and is used as a biocide

in duct-cleaning services

Potential human health effects associated with glutaraldehyde exposureshave been reported (case reports, field investigations, limited epidemiolog-ical studies, challenge, and animal studies) These have included irritantsymptoms of the nose and throat and other symptoms such as nausea andheadache They have also included pulmonary symptoms such as chesttightening and asthma Other exposure concerns include reproductive effectsand cancer Limited studies suggest that exposure to glutaraldehydeincreases the risk of spontaneous abortion among pregnant females Cancerrisks have been inferred from chemical reactivities and mutagenic activity

of similar compounds However, there is no direct evidence that hyde is either an animal or human carcinogen

glutaralde-II VOCs/SVOCs

A number of studies have been conducted to both identify and quantify VOCs

in indoor environments Despite inherent difficulties in sampling and fying VOCs present in mixtures at low concentrations, available evidence indi-cates that a large and variable number of VOCs are present in indoor air VOCcompounds vary widely from building to building, depending on sourcespresent as well as human activities Studies conducted to date have reportedthe presence of many different aliphatic and aromatic hydrocarbons and hydro-carbon derivatives such as oxygenated and halogenated hydrocarbons

identi-The aldehydes are a group of VOCs that have received special attention

in indoor environments because of their irritant effects at relatively lowconcentrations The aldehydes, however, represent only a fraction of a largergroup of organic compounds found to contaminate air in residential andnonresidential indoor environments Concentrations of individual VOCs andSVOCs as described below are very low and, therefore, it is generallybelieved that exposure to any individual VOC (other than HCHO) poseslittle or no risk of causing acute symptoms in building occupants Neverthe-less, because of the large number of VOCs, and to a lesser extent SVOCs,present, health concerns have been expressed relative to the collective effect(i.e., additive, synergistic) of exposures to a large number of substances, aswell as substances which are potentially carcinogenic in humans

A VOCs in residential buildings

VOCs detected and quantified in U.S residences include aromatic bons such as toluene, ethyl benzene, m- and p- isomers of xylene, naphtha-lene, and methylnapthalene, alkanes such as nonane, decane, undecane,dodecane, tridecane, tetradecane, pentadecane, and hexadecane, as well ascompounds such as mesithylene, cumene, limonene, and benzaldehyde Tol-uene was observed in the highest concentrations (45 to 160 µg/m3) With theexceptions of toluene, xylene, and benzaldehyde, average concentrations ofother individual VOCs were <20 µg/m3

hydrocar-Volatile organic compounds and their levels have been characterized inhundreds of randomly selected German houses The 57 individual VOCsidentified included straight (n-), branch-chained, and cyclic alkanes, aro-matic hydrocarbons, chlorinated hydrocarbons, terpenes, carbonyls, andalcohols Concentration ranges of individual compounds varied by threeorders of magnitude With the exception of toluene, mean concentrationswere <25 µg/m3, with most <10 µg/m3 (low ppbv range expressed as mixingratios) The average sum of identified VOCs was approximately 0.4 mg/m3,with a range of 0.07 to 2.67 mg/m3 In a study of new and older occupiedapartments, Danish investigators reported summed VOC concentrations innewer apartment units to average 6.2 mg/m3 and 0.4 mg/m3 in older units

B VOCs in nonresidential buildings

A number of investigations have been conducted to characterize VOCs innonresidential buildings such as offices, schools, and other institutional envi-ronments Concentrations of individual VOCs in California office buildingshave been reported to range from 3 to 319 µg/m3 Major identified com-pounds included straight, branch-chained, and cyclic alkanes, followed by

a variety of aromatic hydrocarbons, with toluene the most common andabundant VOC Chlorinated hydrocarbons, such as tetrachloroethylene,1,1,1-trichloroethane, and trichloroethylene, were also commonly measured

In qualitative and quantitative analyses of air samples collected from

public access buildings, USEPA identified hundreds of aliphatic

hydrocar-bons as well as 200 or so other organic compounds These included aromatic

hydrocarbons, halogenated hydrocarbons, esters, alcohols, phenols, ethers,

ketones, aldehydes, and epoxides Concentrations in new buildings were

generally much higher than in established or older buildings, often by an

order of magnitude or more

As a part of its BASE (Building Assessment Survey Evaluation) study,

USEPA conducted VOC/SVOC measurements in 56 randomly selected

pri-vate office buildings The frequency of detected VOCs/SVOCs is

summa-rized in Table 4.7 Thirty-four VOCs were detected in 81+% of samples

collected Concentrations of 12 VOCs observed at the highest concentrations

are summarized in Table 4.8 The highest median concentrations were

observed for acetone, toluene, d-limonene, xylenes, 2-butoxyethanol, and

n-undecane With the exception of d-limonene (used as a fragrance), these

substances are commonly used as solvents and tend to be in the highest

concentration range

Table 4.7 Frequency of Detected VOCs/SVOCs in the USEPA BASE Study

of 56 Randomly Selected Office Buildings

VOCs

Frequency = 81 to 100%

Styrene m- and p-Xylene TXIB

n-Undecane 4-Ethyltoluene n-Dodecane

2-Butoxyethanol Nononal 2-Ethyl-1-hexanol

Benzene n-Hexane 1,1,1-Trichloroethane

Ethylbenzene α -Pinene 1,2,4-Trimethylbenzene

Texanol 1 and 3 Tetrachloroethane 4-Methyl-2-pentanone

Trichloro-trifluoroester Chloroform Carbon tetrachloride

4-Phenycyclohexene Carbon disulfide Chlorobenzene

1,2,4-Trichlorobenzene 1,2-Dichlorobenzene

Source: From Girman, J.R et al., Proc Indoor Air ‘99, Edinburgh, 2, 460, 1999.

Mean (and median) concentrations of VOCs of individual compounds

in nonresidential buildings tend to be below 50 µg/m3, with most below

5 µg/m3 Volatile organic compounds in nonresidential buildings are fewer

in number than those found in residences but are qualitatively similar

Con-centrations tend to be lower (by as much as 50% or more) both on an

individual basis and TVOC (total volatile organic compounds) levels

C Sources/emissions

Investigators in North America and Europe have attempted to characterize

emissions of VOCs from building materials and consumer products VOC

emissions from such products/materials vary with the product as well as

with its manufacturer Major VOCs emitted from a sample of products are

identified in Table 4.9

Most compounds listed in Table 4.9 are nonpolar substances Polar

sub-stances, on the other hand, are commonly used in a variety of personal and

home-care products such as colognes, perfumes, deodorants, soaps,

deter-gents, shampoos, air fresheners, and cosmetics In a study of these materials,

USEPA observed that polar compounds such as ethanol, benzaldehyde, α

-terpineol, and benzyl acetate were found in over 50% of 31 products tested

In an intensive study of five products (two colognes, one perfume, one soap,

and one air freshener), USEPA confirmed the presence of the above four

compounds as well as α-pinene, β-pinene, camphene, myacene, limonene,

diethylene glycol monomethyl ether, linalool, β-phenethyl alcohol, benzyl

alcohol, estragole, and menethyl acetate in one or more products, with

limonene and linalool found in all five products tested

Table 4.8 Median and Maximum Concentrations of 12 VOCs Observed at

the Highest Concentrations in the USEPA BASE Study of 56 Randomly

Selected Office Buildings VOC

Median concentration ( µ g/m 3 )

Maximum concentration ( µ g/m 3 )

As is the case with HCHO, source emissions decrease rapidly with time.Higher temperature and ventilation rates significantly increase emissionrates and thus accelerate decay rates Decay rates of individual compoundsdecrease very rapidly with time, as can be seen with a wet (freshly appliedfinish coating) and dry (carpeting) product (Figures 4.3 and 4.4).

Time-dependent decreases in VOC concentrations have been reported

in source emission studies In newly built Swedish preschool buildings, morethan 50% of 160 different compounds initially identified were undetectablewithin a 6-month period Similar declines in VOC concentrations have alsobeen observed by USEPA

D Polyvalent alcohols and their derivatives

Manufacturers have significantly reduced solvent levels in paints, varnishes,and adhesives during the past decade These water-based products emit lowlevels of low-volatility VOC compounds which are being used both assolvents and dispersants Most commonly they are highly polar ether orester derivatives of polyvalent alcohols, with boiling points in the range of

125 to 255°C

These compounds include glycol, glycol–ethers, and associated acetates(esters formed by reaction of an alcohol with acetic acid) They are chemicallystable, colorless, and inflammable liquids with an ethery to sweetish odor.They are miscible with water and organic solvents

Table 4.9 VOCs Emitted from Building Materials and Consumer Products Material/product Major VOCs identified

Latex caulk Methylethylketone, Butyl propionate, 2-Butoxyethanol,

Butanol, Benzene, Toluene Floor adhesive Nonane, Decane, Undecane, Dimethyloctane, 2-

Methylnonane, Dimethylbenzene Particle board Formaldehyde, Acetone, Hexanal, Propanol, Butanone,

Benzaldehyde, Benzene Moth crystals p-Dichlorobenzene

Floor wax Nonane, Decane, Undecane, Dimethyloctane,

Trimethylcyclohexane, Ethylmethylbenzene Wood stain Nonane, Decane, Undecane, Methyloctane,

Dimethylnonane, Trimethylbenzene Latex paint 2-Propanol, Butanone, Ethylbenzene, Propylbenzene,

1,1-Oxybisbutane, Butylpropionate, Toluene Furniture polish Trimethylpentane, Dimethylhexane, Trimethylhexane,

Trimethylheptane, Ethylbenzene, Limonene Polyurethane floor finish Nonane, Decane, Undecane, Butanone, Ethylbenzene,

Dimethylbenzene Room freshener Nonane, Decane, Undecane, Ethylheptane, Limonene,

substituted aromatics (fragrances)

Source: From Tichenor, B.A., Proc 4th Internatl Conf Indoor Air Qual Climate, Berlin, 1, 8, 1987.

Figure 4.3 TVOC emission decay of a wet (oil-based paint) product (Data extracted from Guo, H., Ph.D thesis, Murdoch University, Perth, Australia, 1999.)

Figure 4.4 TVOC emission decay of a dry (carpeting) product (Data extracted from Guo, H., Ph.D thesis, Murdoch University, Perth, Australia, 1999.)

Ethylene glycol, diethylene glycol, propylene glycol, and their tives are commonly used in paints, varnishes, adhesives, and other products.Concentrations of polyvalent alcohol compounds measured at detectablelevels in German apartments are summarized in Table 4.10 Total glycolcompound concentrations higher than 100 µg/m3 were found in 30 (half hadbeen recently renovated) out of 200 apartments.

deriva-Concentrations of polyvalent alcohols and their derivatives in indoorair are relatively low (because of their low vapor pressures) However,emissions continue for longer periods of time than for more volatile VOCs.Ethylene glycol emissions from latex paint do not show the rapid declinesobserved for higher boiling point VOCs (Figure 4.5) As a consequence,product emissions of polyvalent alcohols and their derivatives may occurfor months or years

E SVOCs

A number of organic compounds present in indoor environments have ing points in the range of 240 to 260°C to 380 to 400°C with vapor pressuresranging from 10–1 to 10–7 mm Hg Such compounds are described as beingsemivolatile organic compounds (SVOCs) They exist in gas and condensedphases (adsorbed to particles) They include a variety of compound typesincluding solvents, linear alkanes, aldehydes and acids, pesticides (discussed

boil-in the followboil-ing section), polycyclic aromatic hydrocarbons (PAHs), chlorinated biphenyls (PCBs), and plasticizers Concentrations of selected

poly-Table 4.10 Glycols/Glycol Derivatives Measured in 200 German Apartments

Compound

Mean concentration (µg/m 3 )

Maximum concentration (µg/m 3 ) Ethylene glycol monomethyl ether 0.8 20.1

Ethylene glycol monoethyl ether 8.1 259.7

Ethylene glycol monophenyl ether 2.3 108

Ethylene glycol monobutyl ether

Diethylene glycol monoethyl ether 1.4 108

Diethylene glycol monobutyl ether 3.0 158

Diethylene glycol monobutyl ether

SVOCs identified in nonresidential Danish buildings are summarized inTable 4.11 Plasticizers were the most common SVOCs measured.

1 Plasticizers

Substances used as plasticizers are ubiquitous contaminants of indoor air andsettled dust They are used in vinyl products to make them soft and relatively

Figure 4.5 Ethylene glycol emissions from latex-based paint (Data extracted from

Roache, N.F et al., in Characterizing Sources of Indoor Air Pollution and Related Sink

Effects, Tichenor, B.A., Ed., ASTM, Conshohocken, PA, 98, 1996.)

Table 4.11 Concentrations of Selected SVOCs Measured in Four Danish Office Buildings, a Day Care Center, and School Classroom During Winter Time

Concentration (ng/m 3 ) Day care

center

School classroom Compound Office 1 Office 2 Office 3 Office 4

phthalate

Source: From Clausen, P.A., Wolkoff, P., and Svensmark, B., Proc Indoor Air ‘99, Edinburgh, 2,

434, 1999.

flexible and typically comprise 25 to 50% of the weight of products such asvinyl floor covering As plasticizers slowly vaporize with time, vinyl productslose their desirable soft properties, become hard and brittle, and crack.Commonly used plasticizers include phthalic acid esters such as dieth-ylhexyl phthalate (DEHP), dibutyl phthalate (DBP), diisobutyl phthalate(DiBP), benzyl butyl phthalate (BBP), and diethyl phthalate (DEP) A com-monly used nonphthalate plasticizer is TXIB (2,2,4-trimethyl-1,3-pentanedioldiisobutryate).

Because of their low vapor pressures, concentrations of individual phase plasticizer compounds in indoor air are generally very low Neverthe-less, significant vapor-phase concentrations may be associated with theinstallation of new building products such as vinyl floor covering or wallpaper where the loading factor is high (high surface to volume ratio) Suchhigh loading factors also occur in new automobiles where the volatilizationand subsequent condensation/deposition of plasticizers is reportedlyresponsible for the “greasy window” phenomenon which is exacerbated bygreenhouse-type heating of automobile interiors on sunny days

vapor-Measurable levels of both vapor- and particulate-phase phthalic acid estershave been reported in buildings Concentrations of DEHP as high as 110 to 230µg/m3 have been associated with emissions from vinyl wall covering, with meanconcentrations of DBP and DiBP in the range of 2 to 16 µg/m3 Air concentrations(vapor and aerosol phase) of phthalate compounds in 125 California residencesare summarized in Table 4.12 These concentrations are approximately half ofthose reported for Danish nonresidential buildings (Table 4.11)

Phthalates associated with airborne and settled dust have been reportedfor Norwegian residences Total phthalate concentrations in suspended par-ticulate matter ranged from 450 to 2260 ppm (w/w) with an average con-centration of 1180 ppm The settled dust concentration of phthalates was 960ppm, with DEHP comprising approximately two thirds of this level Sus-pended and settled dust levels were strongly correlated, particularly forDEHP and DBP As such, resuspended settled dust appears to be the majorroute of human exposure

TXIB, a nonphthalate plasticizer, has been reported in the concentrationrange 100 to 1000 µg/m3 in problem buildings It was one of the most

Table 4.12 Concentrations of Phthalate Compounds Measured in 125

California Residences Concentration (ng/m 3 ) Indoor/outdoor

ratio Compound Median 90th percentile

common substances detected in nonresidential U.S buildings (frequency 81

to 100% in 56 BASE office buildings), with concentrations in the range of 0.2

to 2.8 µg/m3; in Danish buildings, concentrations were 1.45 to 5.9 µg/m3

(Table 4.11)

2 Nonplasticizer SVOCs

A variety of nonplasticizer SVOCs are found in indoor air in measurableconcentrations (Table 4.11) Texanol, found in the highest concentration, is acolorless liquid mixture, with 2,2,4-trimethyl-1,3-pentanediol monoisobu-tyrate, a compound closely related to TXIB, the dominant compound present

It is commonly added to latex-based paints and has a vapor pressure of0.013 mm Hg

3 PCBs

Polychlorinated biphenyls (PCBs) are a group of synthetic chemical pounds (209) characterized by the attachment of one to 10 chlorine atoms to

com-a biphenyl moiety They were produced in the U.S from com-approximcom-ately 1930

to the mid-1970s and marketed under the trade name Arochlor™ rinated biphenyls were used as: dielectric fluids in transformers and capac-itors, heat transfer and hydraulic fluids, lubricating and cutting oils, andplasticizers in adhesives They were also used in paints, pesticides, inks,caulking, and sealants As a consequence, PCBs are ubiquitous contaminants

Polychlo-of many pre-1975 buildings

Polychlorinated biphenyls represent a number of building tion concerns These include fluorescent light ballast leakage and failureswhich result in air and surface contamination Polychlorinated biphenyllevels in buildings with PCB-containing transformers (191–888 ng/m3) havebeen observed to be twice as high as those without such transformers.Polychlorinated biphenyl contamination of building surfaces, as well asair, is a particularly significant problem when a building has experienced astructural fire Fire can destroy dozens, if not hundreds, of PCB-containingballasts Resulting surface contamination poses a significant challenge tobuilding owners and restoration personnel in their efforts to restore the fire-damaged/contaminated areas and materials Air and surface PCB levels must

contamina-be contamina-below guideline values to make the building acceptable for reoccupancy

In one building subjected to a limited structural fire, elevated air andsurface PCB levels were reported to be associated with (1) PCB-containingadhesive used to adhere fiberglass insulation to the exterior of metal supplyair ducts and (2) the adhesive of fiberglass duct board The burned buildingwas also contaminated with polychlorinated dibenzofurans, polychlorinated

dibenzo-p-dioxins, and combustion products of PCBs.

4 Floor dust

Low-volatility, high-potency organic compounds and those with high ity can be expected to partition more to particles than to the vapor phase in