Tobacco smoke in the workplace: an occupational health hazard

Tobacco smoke in the workplace:an occupational health hazard

Neil E. Collishaw,* MAJohn Kirkbride,t MD, MScDonald T. Wigle,* MD, PhD, MPH

Tobacco smoke, which contains over50 known carcinogens and manyother toxic agents, is a health hazardfor nonsmokers who are regularlyexposed to it while at work. Involun-tary exposure to tobacco smoke an-noys and irritates many healthy non-smokers. Serious acute health effectsare probably limited to the one fifthof the population with pre-existinghealth conditions that are aggravatedby exposure to tobacco smoke. Theconsequences of long-term exposureinclude decreased lung function andlung cancer. Existing air qualitystandards for workplaces do not di-rectly specify an acceptable level fortobacco smoke. The evidence on thecomposition of tobacco smoke andon the health hazards of involuntaryexposure suggests that there may notbe a "safe" level for such exposure.

La fumee du tabac, qui renferme plusde 50 substances cancerogenes con-nues et de nombreux autres agentstoxiques, met en danger la sante desnon-fumeurs qui y sont regulierementexposes au travail. L'expositioninvolontaire a la fumee du tabacrepresente une source d'ennuis et

From the Department of National Healthand Welfare, Ottawa

*Chief, policy analysis, Bureau of TobaccoControl, Health Protection BranchtDirector, Occupational Health Unit, Medi-cal Services Branch4Chief, Non-Communicable Disease Divi-sion, Bureau of Epidemiology, Health Protec-tion Branch

Reprint requests to: Neil E. Collishaw, Bu-reau of Tobacco Control, Health ProtectionBranch, Department of National Health andWelfare, Tunney's Pasture, Ottawa, Ont.KIA OL2

d'irritation pour de nombreux non-fumeurs en bonne sante. Des malai-ses aigus graves sont vraisemblable-ment limites au cinquieme de lapopulation accusant des problemesde sante preexistants que l'expositiona la fumee du tabac aggrave. Parmiles consequences de l'exposition along terme notons la diminution dela fonction pulmonaire et le cancerdu poumon. Les normes actuelles dequalite de l'air aux lieux de travail nes'adressent pas directement a laquestion d'un niveau acceptable de lafumee du tabac. Les donnees sur lacomposition de la fumee du tabac etsur les risques de l'inhalation invo-lontaire pour la sante laissent enten-dre qu'il se peut qu'il n'y ait pas deniveau "suir" d'exposition a la fumeedu tabac sur les lieux de travail.

There are standards for limiting oc-cupational exposure to many air-borne toxic substances. Thresholdlimit values (TLVs) are the maxi-mum time-weighted average concen-trations to which workers can beexposed in a normal 8-hour workdayor a 40-hour workweek. The Ameri-can Conference of Governmental In-dustrial Hygienists Inc. (ACGIH)has published the TLVs for over 500toxic substances,' including severalthat are in tobacco smoke, but nonefor tobacco smoke per se.The inhalation by nonsmokers of

air contaminated by tobacco smokeis referred to as involuntary expo-sure. Such air contains the sametoxic chemicals present in "main-stream smoke" (that inhaled by asmoker during a puff). However, themain source of tobacco smoke con-taminants is "sidestream smoke"(that emitted by the burning tip of acigarette, cigar or pipe), which con-tains much higher concentrations ofmany toxic and cancer-causingchemicals than does mainstreamsmoke2 (Table I).

It has been estimated that 63% ofthe labour force in the United Statesis exposed to tobacco smoke in theworkplace.3 The proportion in Cana-da is likely to be higher because ofthe higher per-capita consumptionof cigarettes.4'5The toxic substances in tobacco-

smoke-polluted air are inhaled and,to varying degrees, absorbed by ex-posed nonsmokers. Tobacco smoke,both sidestream and mainstream, isa concentrated aerosol of very smallparticles measuring less than 0.6 ,umin mass median aerodynamic diame-ter.6 It has been predicted that 30%to 40% of these particles will depositin alveolar regions and 5% to 10% inthe tracheobronchial region.7 Suchparticles contain many known car-cinogens;2'8 they may be engulfed bymacrophages or transported to re-gional lymph nodes and may takedays to months to clear from thelungs.9

Composition of tobacco smoke

Tobacco smoke is a complex mix-ture of particles and gases that con-tain at least 3800 different chemicalcompounds,'" over 50 of which areknown to be carcinogenic in animalsor humans or both. Little is knownabout the health effects of most ofthe 3800 chemicals, and almostnothing is known about their inter-active effects.

Gas phase

About 90% by weight of tobaccosmoke is in the gas phase. Themajor toxic element by weight iscarbon monoxide. The visible smokefrom the tip of a burning cigarettecontains relatively high concentra-tions of toxic chemicals that becomeslightly diluted as the smoke driftshorizontally for distances up to 3 m.Nonsmokers who are located close

CAN MED ASSOC J, VOL. 131, NOVEMBER 15, 1984 1199- For prescribing information see page 1303

to smokers are exposed to the irri-tants formaldehyde and acrolein atconcentrations of up to 110 and 70parts per million (ppm) respective-ly.'"The gas phase also contains other

irritants (e.g., ammonia, nitrogenoxides and pyridine), ciliatoxicagents (e.g., hydrogen cyanide) andseveral potent carcinogens (e.g., N-nitrosodimethylamine). The toxicsubstances in the gas phase are notremoved by standard air filtrationsystems.

Particulate phase

This is a highly concentratedaerosol containing about 5 X 1 09particles per millilitre of mainstreamsmoke.8 Particles of sidestreamsmoke have a smaller geometricmean diameter (0.20,um) than thoseof mainstream smoke (0.36 Mm).12Thus, a higher proportion of side-stream particles would be expectedto deposit in alveolar regions.

Risks of involuntary exposure totobacco smoke

The serious health consequencesof smoking have been well knownfor many years and have been sum-

marized in recent reports of the USsurgeon general.27'8'3 However, theeffect of tobacco smoke on thehealth of nonsmokers is a matter ofgrowing concern; it was reviewed insome detail in the most recent reportof the US surgeon general7 andmerits closer examination here.

Physiological changes andsubclinical toxic effects

Eye irritation, the most commoncomplaint of healthy people exposedto tobacco smoke, and the rate ofeye blinking increase with increasingamounts or duration of exposure tosmoke.' After 1 hour's exposure tosmoke-related carbon monoxide atconcentrations as low as 1.3 ppm,well within those measured underrealistic conditions, eye irritationand the rate of blinking increasesignificantly.7

Brief exposure of nonsmokingadults to high concentrations of to-bacco smoke under carefully con-trolled conditions in exposure cham-bers results in a small but significantimpairment of lung function, includ-ing maximal airflow at 50% and75% of forced vital capacity, Vmax50and Vmax75.7

Involuntary exposure to tobacco

smoke increases the heart rate andblood pressure in patients with angi-na pectoris.'4

Relatively low concentrations ofcarbon monoxide, similar to those inconfined, smoky areas, significantlyimpair one's driving (e.g., by redu-cing braking time and delaying re-covery of vision following glare).'5

Symptoms

The symptoms reported by non-smokers exposed to tobacco smokeinclude eye irritation, nasal conges-tion, headache, cough, sore throat,hoarseness, nausea, dizziness, "gen-eral annoyance", loss of appetiteand Raynaud's phenomenon.'6"23

Aggravation ofpre-existingconditions

The results of the Canada HealthSurvey indicate that 21% of Canadi-ans have a health condition that isaggravated by exposure to tobaccosmoke.24 These conditions includeheart disease, acute respiratory dis-ease, emphysema, asthma and hayfever. Persons who wear contactlenses also experience eye irritation,but the number of such persons inCanada is not known.

1200 CAN MED ASSOC J, VOL. 131, NOVEMBER 15, 1984

toxic and tumourigenic agents in cigarette smoke and their ratio in mainstreamTable I Concentrations of the majorsmoke (MS) and sidestream smoke (SS)'Phase and agent(s) MS level SS/MS ratio* Phase and agent(s) MS level SS/MS ratio*

Gas Stigmasterol 53,ug 0.8Carbon dioxide 10-80 mg 8.1 Total phytosterols 130 gg 0.8Carbon monoxide 0.5-26 mg 2.5 Naphthalene 2.8 ug 16Nitrogen oxides 16-600ug 4.7-5.8 1-methylnaphthalene 1.2,ug 26Ammonia 10-130 gg 44-73 2-methylnaphthalene 1.0,ug 29Hydrogen cyanide 280-550,ug 0.17-0.37 Phenanthrene 2.0-80 ng 2.1Hydrazine 32,ug 3 Benz(a)anthracene 10-70 ng 2.7Formaldehyde 20-90,ug 51 Pyrene 15-90 ng 1.9-3.6Acetone 100-940 ug 2.5-3.2 Benzo(a)pyrene 8-40 ng 2.7-3.4Acrolein 10-140ug 12 Quinoline 1.7,ug 11Acetonitrile 60-160ug 10 Methylquinoline 6.7,ug 11Pyridine 32,ug 10 Harmane 1.1-3.1,g 0.7-2.73-vinylpyridine 23,ug 28 Norharmane 3.2-8.1,ug 1.4-4.3N-nitrosodimethylamine 4-180 ng 10-830 Aniline 100-1200 ng 30N-nitrosoethyl- o-toluidine 32 ng 19

methylamine 1.0-40 ng 5-12 l-naphthylamine 1.0-22 ng 39N-nitrosodiethylamine 0.1-28 ng 4-25 2-naphthylamine 4.3-27 ng 39N-nitrosopyrrolidine 0-110 ng 3-76 4-aminobiphenyl 2.4-4.6 ng 31

Particulate N-nitrosonornicotine 0.2-3.7,ug 1-5Total 0.1-40 mg 1.3-1.9 4(methyinitrosamino)-1-Nicotine 0.06-2.3 mg 2.6-3.3 (3-pyridyl)-1-butanone 0.12-0.44,ug 1-8Toluene 108sg 5.6 N-nitrosoanatabine 0.15-4.6,ug 1-7Phenol 20-150,ug 2.6 N-nitrosodiethanolamine 0-40,ug 1.2Catechol 40-280,ug 0.7 Polonium 210 0.03-0.5 pc NA

*NA = not available.

Persons with angina have a sub-stantially increased susceptibility toexercise-induced attacks when theyare exposed to low concentrations oftobacco smoke.'4 Persons with asth-ma experience attacks (wheezingand difficulty in breathing) whenexposed to tobacco smoke;2526 it isnot clear whether tobacco smokeacts as an allergen, an irritant orboth.

Acute illnesses

Available evidence on the role ofinvoluntary exposure to tobaccosmoke in acute respiratory tract in-fections is based on studies of chil-dren so exposed in their homes.Bronchitis, pneumonia and otherrespiratory illnesses have been foundto occur more frequently amonginfants and children up to 2 years ofage who have one or two parentswho smoke.7 Several of the studiesreviewed by the US surgeon general-revealed an exposure-response rela-tion between the amount of parentalsmoking and the risk of respiratoryillness. Young children may general-ly be more susceptible than adults,but it seems likely that exposure totobacco smoke in the workplacewould also increase the risk of acuterespiratory illnesses in adults, par-ticularly those with predisposinghealth problems, such as heart dis-ease or allergies.

Long-term effects

A study of 2100 adults revealedimpairment of small-airways func-tion in nonsmokers who were em-ployed for at least 20 years in en-closed work areas where smokingwas permitted.27 The loss of functionwas equivalent to that in personswho had smoked up to 10 cigarettesper day for at least 20 years. Aswell, the amount of particulate mat-ter inhaled by nonsmokers is equiva-lent to that inhaled by persons whosmoke up to 10 cigarettes per dayand is sufficient to produce seriouslung damage.28A recent study of almost 8000

adults in France indicated that non-smokers of either sex who were 40years of age or older and whosespouses had smoked at least 10 g oftobacco (i.e., about 10 cigarettes)per day had impairment of lung

function that was not explainable bysocial class, education, air pollutionor family size.29 The average degreeof impairment was 16% for men and6% for women. Although not relatedto workplace, it is interesting thatimpairment of small-airways func-tion has also been observed in chil-dren whose mothers smoked.30

Several studies have shown anincreased risk of lung cancer amongnonsmokers who are married tosmokers.3'34 Indeed, the risk was upto 3.4 times that among persons notexposed to tobacco smoke. Anotherstudy revealed only a slight, statisti-cally insignificant increase in therisk of lung cancer among womenwho did not smoke but were marriedto men who did.35 However, thisfinding is weakened by the fact thatmarital status and the spouse'ssmoking habits are a poor index ofexposure to tobacco smoke forAmerican women since many ofthem work outside the home.36 Re-pace37 noted that the failure to ad-just for exposure to tobacco smokein the workplace probably resultedin an underestimate of the effect ofinvoluntary exposure in the home.

Hirayama38 reported standardizedmortality ratios for nasal sinus can-cer among women who did notsmoke of 1.0, 2.3, 2.6 and 3.3 whentheir husbands were nonsmokers orsmokers of 1 to 14, 15 to 19, or 20or more cigarettes daily respectively.

Interaction between involuntary andoccupational exposures

This topic was critically reviewedin the 1979 report of the US sur-geon general under the generalheading of smoking and occupation-al exposures.8 The report noted thatcertain toxic agents in tobaccosmoke may also be present in theworkplace, thus increasing the likeli-hood of exposure to the agent. Forexample, hydrogen cyanide is pres-ent in cigarette smoke at concentra-tions of up to 1600 ppm. Otherexamples include carbon monoxide,methylene chloride, acrolein, arse-nic, formaldehyde and polycycliccomponents. Given that the risk oflung cancer is greatly increasedamong workers who smoke ahd areexposed to asbestos,39 it is highlyprobable that exposure to air con-taminated by both tobacco smoke

and asbestos is a greater hazardthan exposure to asbestos alone fornonsmokers. This inference is basedon the fact that all of the chemicalsin mainstream smoke are also insidestream smoke; indeed, the con-centrations are often much higher inthe latter.

Estimates of exposure to tobaccosmoke among nonsmokers

Biologic indicators

The chemicals present in tobaccosmoke, or their metabolites, havebeen repeatedly detected in samplesof blood, urine, saliva and breastmilk from nonsmokers.46 Russelland Feyerabend4' concluded that, asa result of involuntary exposure totobacco smoke, most nonsmokers inurban areas have measurableamounts of nicotine in their bodyfluids for most of their lives. In onestudy nicotine levels were measuredin saliva and urine samples fromhospital employees after a morningat work.42 The nonsmokers who had-been exposed to tobacco smoke hadsignificantly higher nicotine concen-trations than those who had notbeen exposed. Mutagenic activityhas been detected in cigarette-smoke-contaminated air and inurine samples from nonsmokers ex-posed to such air.45 In another studytrace amounts of nicotine and coti-nine (formed in the body from nico-tine) were detected in samples ofbreast milk from three nonsmokerswho were exposed to tobacco smokeat work but not at home;46 theconcentration of these substancesfell to unmeasurable levels on week-ends.

Levels of tobacco smoke in ambientair

Using data from American timeuse and smoking surveys, Repaceand Lowrey3 estimated the propor-tion of nonsmokers who are likely tobe chronically exposed to tobaccosmoke at work or at home, or both,to be 86% (Table II). In the UnitedStates it was estimated that, in1980, smokers constituted 34% ofthe adult population and smoked anaverage of 22 cigarettes per day.'3 InCanada in 1981 both the proportionof smokers and the average number

CAN MED ASSOC J, VOL. 131, NOVEMBER 15, 1984 1201

of cigarettes smoked daily werehigher (39% and 27 respectively).4Canada has the highest rate of use

of manufactured cigarettes amongindustrialized nations.5 Moreover, it

is likely that Canadians, who gener-ally face more severe climatic condi-tions than Americans, spend more

time indoors. Therefore, Repace andLowrey's estimates of the proportionof American nonsmokers exposed totobacco smoke indoors can beviewed as conservative estimates ofthe proportion of Canadian non-

smokers so exposed.

Air quality standards

In Canada the standards set bythe ACGIH are usually used tojudge air quality in the workplace."47However, to date the ACGIH hasprovided neither recommendationsnor documentation pertaining to a

TLV for tobacco smoke per se.

TLVs and related documentationare provided primarily for identifi-able chemical substances that are

closely associated with industrialprocesses.Tobacco smoke is a complex mix-

ture of particles and gases, and theACGIH suggests a formula for de-termining the TLVs for mixtures.47The air quality standard is deemednot to have been exceeded if

n .Ci< 1

iTi

where C is the observed concentra-tion of the dangerous substance i,and T is the listed TLV for thatsubstance. The TLV of a mixture ofdangerous substances is to be ap-

plied only when the componentshave similar toxicologic effects andwhen the concentrations and sources

of the dangerous substances areknown. Unfortunately, the toxico-logic effects of many of the chemi-cals in tobacco smoke are poorlyunderstood. In the numerous investi-gations to determine the concentra-tions of various toxic substances intobacco smoke in indoor air, theconditions under which the measure-

ments were obtained differed great-ly.48 Therefore, the calculation of an

exact TLV for tobacco smoke isdifficult. Nevertheless, enough isknown about the effect of tobacco

smoke on indoor air for the USNational Research Council to haveconcluded that "public policy shouldclearly articulate that involuntaryexposure to tobacco smoke has ad-verse health effects and ought to beminimized or avoided where possi-ble".48When there are a number of

harmful substances it is frequentlyonly feasible to evaluate the hazardsby measuring a single substance. Insuch cases the ACGIH47 recom-

mends that "the threshold limit usedfor this substance should be reducedby a suitable factor, the magnitudeof which will depend on the number,toxicity and relative quantity ofother contaminants ordinarily pres-ent". To determine a suitable TLVfor tobacco smoke a more detailedexamination is needed of the knownhealth effects of and the recom-mended exposure limits for some ofthe substances in tobacco smoke.

In smoky areas with minimal ven-

tilation the TLV for carbon monox-ide may be exceeded, but even a

modest increase in the amount ofventilation results in a rapid fall inthe carbon monoxide level. The airconcentrations of carbon monoxideand other contaminants from tobac-co smoke are often measured atsome distance from the nearestsmoker and thus tend to be lowerthan those to which persons workingclose to smokers are exposed.8 Car-bon monoxide concentrations of upto 29 ppm were found in work areas

where smoking was permitted;27 thislevel is below the TLV (50 ppm) butwell above the Ambient Air QualityStandard48 (the US standard foroutdoor air in cities) of 9 ppm.

There are at least 38 known or

probable carcinogens in the particu-

late phase and another 16 in thevolatile phase of tobacco smoke.2'8'49The eight volatile N-nitrosaminesare largely retained by the smokeparticulates in the glass fibre filtersthat are used to separate the twophases. The carcinogenicity of to-bacco smoke particulates in animalsexceeds that expected from a sum-

mation of the carcinogenicity of theindividual known carcinogens.2 Thisis probably due, at least in part, tothe presence of many tumour pro-moters and cocarcinogens in the vol-atile phase. For example, catechol isa known cocarcinogen and is themain phenolic compound in tobaccosmoke, its concentration being 20 to460 ug per cigarette.2Most of the cancer-causing and

other toxic chemicals in tobaccosmoke are formed in a pyrolysis-distillation zone just behind theheat-generating combustion zone.2

The concentration of toxic chemicalsis higher in sidestream than in main-stream smoke because the tempera-ture of the burning tip of a cigaretteor cigar that is not being smoked islower; hence, combustion is lesscomplete than during a puff.2

Table III lists the known andprobable carcinogens in tobaccosmoke. The ACGIH lists acryloni-trile and vinyl chloride as knownhuman carcinogens with assignedTLVs of 4.5 and 10 mg/m3 respec-tively.' Two other chemicals,2-naphthylamine and 4-aminobi-phenyl, are listed as known humanbladder carcinogens to which "noexposure or contact by any routerespiratory, skin or oral, as detectedby the most sensitive methodsshall be permitted".47 Althoughthese two substances are known tobe present in very small quantities in

1202 CAN MED ASSOC J, VOL. 131, NOVEMBER 15, 1984

Table II-Estimated daily annual average exposure of nonsmokers to tobaccosmoke at work and at home3

Estimated amount ofparticulate phaseinhaled daily (mg)

Probability of exposure Probability-Exposure site (rounded values, %)* Average weighted average

Work and home 63 X 62 = 39 2.27 0.89Neither work nor home 37 X 38 = 14 - -Work only 38 X 63 = 24 1.82 0.44Home only 37 X 62 = 23 0.45 0.10

Total 100 1.43

sidestream smoke, studies of theirconcentration in ambient air con-

taining tobacco smoke have not yetbeen reported.The International Agency for Re-

search on Cancer (IARC) lists arse-

nic, benzene, and soots, tars andoils, as well as "whole tobaccosmoke", as known human carcino-gens.49 Both the ACGIH and theIARC consider benzo(a)pyrene,formaldehyde and hydrazine as

probably carcinogenic to humans on

the basis of repeated demonstrationsof carcinogenesis in animals and thelimited evidence of carcinogenesis inhumans. The IARC also lists nickeland cadmium as probable humancarcinogens. The ACGIH considersN-nitrosodimethylamine as probablycarcinogenic and recommends "thatexposures be avoided, insofar as pos-sible, or otherwise be kept to an

absolute minimum".' Brunnemannand Hoffmann50 have detected N-nitrosodimethylamine at concentra-tions of 0.11 to 0.24 ,ug/m3 in ambi-ent air contaminated with tobaccosmoke.The ACGIH also lists TLVs for

most of the other toxic agents intobacco smoke shown in Table I.

The TLVs are also given for many

other toxic substances, such as nick-el, cadmium and arsenic (Table III).However, because tobacco smoke isa mixture of substances all the

TLVs should be reduced by an un-

known amount.The ACGIH has suggested a

TLV of 5 mg/m3 for respirable nui-sance particulates.' However, thiscategory was defined to includedusts that have a long history oflittle adverse effect on the respirato-ry system. Neither the IARC nor

the ACGIH has made specific refer-ence to the particulate phase oftobacco smoke.Repace and Lowrey3 have given

the total suspended particulate con-

centrations for 56 indoor locations.In all 23 areas where tobacco smokewas present the US National Ambi-ent Air Quality Standard, 75pg/m3,4' and the Canadian NationalAir Quality Objective, 70 ,ug/m3,5'both outdoor air standards for time-weighted annual exposure to totalsuspended particulates, were exceed-ed. These 23 cases involved short-term time-averaged measurementsof total suspended particulate con-

centrations, and the 24-hour stan-dards were exceeded in only a fewcases. However, Repace and Lo-wrey2' have argued that in each ofthe 23 areas there would be repeatedviolations of the 24-hour standardand almost certainly repeated viola-tion of the annual standard. In all33 locations where tobacco smokewas not present the concentrationsof total suspended particulates were

well within both the United States'and Canada's standards. From thesefindings Repace and Lowrey3 haveestimated that nonsmokers are ex-

posed to an average of 1.43 mg oftobacco smoke particulates per day(Table II).

In another investigation Repaceand Lowrey'2 analysed data on theconcentrations of tobacco smokeparticulates in the workplace, therisk of such exposure and the effectof ventilation on indoor air quality.Standards of lifetime involuntarycarcinogenic risk to the public thatare used by the US Food and DrugAdministration and the US Environ-mental Protection Agency rangefrom 10 ` to 10 `. Repace andLowrey52 assumed a 10` risk forlifetime involuntary exposure

to tobacco smoke and calculat-ed the resulting maximum permissi-ble annual average of daily exposureto tobacco smoke particulates in theworkplace to be 0.75 ,ug/m3. Thecurrent published air quality stan-dards do not list precise thresholdlimit values for tobacco smoke par-ticulates. However, in average con-

ditions the actual concentration oftobacco particulates in a typical of-fice was estimated to be about 200Sug/m.a52

Summary

Several authoritative agencieshave reviewed the scientific evidenceconcerning involuntary exposure totobacco smoke and have concludedthat it is a health hazard to beavoided if possible. These agenciesinclude the US Surgeon General'sOffice,2'7 the US National ResearchCouncil,4` the Ontario Council ofHealth's Task Force on Smoking53and the Ontario Medical Associa-tion (The Citizen, Ottawa, Mar. 31,1983: page 18).Repace and Lowrey52 have pro-

posed a threshold limit value fortobacco smoke particulates that ismuch lower than the existing ob-served levels in office accommoda-tions. Our review of recommendedlimits of exposure in the workplaceto the known and probable carcino-gens in ambient tobacco smoke re-

vealed that there are no publishedlimits of exposure to tobacco smokeper se. However, for several of thecomponents in tobacco smoke the

CAN MED ASSOC J, VOL. 131, NOVEMBER 15, 1984 1203

Table 111-Known and probable human carcinogens in tobacco smoke, asdetermined by the American Conference of Governmental Industrial HygienistsInc. (ACGIH)' and the International Agency for Research on Cancer (IARC)49

Status, according toACGIH or IARC or both, Threshold

of carcinogenTheolof carcinogen limit value (mg/m3)Carcinogen Known Probable assigned by ACGIH

Acrylonitrile ACGIH 4.5Vinyl chloride IARC, ACGIH 102-naphthylamine IARC, ACGIH 04-aminobiphenyl IARC, ACGIH 0Arsenic IARC 0.2Benzene IARC ACGIH 30Soots, tars and oils IARC Not assignedWhole tobacco IARC Not assignedsmoke

Benzo(a)pyrene IARC, ACGIH Not assignedFormaldehyde IARC, ACGIH 1.5Hydrazine IARC, ACGIH 0.1N-nitrosodimethyl- ACGIH Not assigned;

amine avoidance of exposurerecommended

Nickel IARC 1.0Cadmium IARC 0.05

recommended exposure limit is ei-ther zero or' not assigned, suggestingthat there may not be a safe levelfor involuntary exposure to tobaccosmoke.

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