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I I a I I A Critical Examination of the OSHA ETS Risk Assessment T.D. Sterling, Professor W.L. Rosenbe,uin, Senior Research Associate ... ....... . J. J. lVeinkain, Professor Faculty of Applied Sciences, School of Computing Science Simon Fraser University Burnaby, British Columbia, Canada, V5A lS6 July 27, 1994

Contents .... . 1 Executive Summary 4 2 Introduction 8 3 Methods 7 3.1 Notation ..................................... 7 ' I 4 I t 5 I I I I 6 7 I I I I 3.2 Outline of the Mathematical Model . . . . . . . . . . . . . . . . . . . . . . 8 OSHA's Risk Estimates 11 4.1 Data Sources . . . . . . . . . . . . . . . . . . . . . . . . ... . 11 4.1.1 The Proportion of Employed Non-Smokers With Workplace ETS Ex- p osure . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . 12 4.1.2 The Relative Risk of Workplace ETS Exposure Among Non-Smokers 12 4.1.3 The Mortality Rates of Employed Non-Smokers . . . . . . . . . . 13 Result of OSHA's Risks Assessment 14 An Evaluation of OSHA's Procedure 15 6.1 The Mathematical Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2 How Appropriate Are the Population Parameter Estimates Utilized in OSHA's -- Mathematical Model? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.2.1 The Proportion of Employed Non-Smokers Exposed to ETS in the Workplace . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . 18 6.2.2 The Relative Risk of Lung Cancer and Heart Disease of Employed Non-Smokers With Workplace ETS Exposure Versus Employed Non- Smokers with no Such Exposure . . . . . . . . . . . . . . . . . . . . 20 6.2.3 The Mortality Rate of Employed Non-Smokers . . . . . . . . . . . . 27 What Can Validly Be Done to Estimate Lifetime Lung Cancer Mortality Risks Associated With Workplace ETS Exposure? 28 7.1 Data Sources . . . . . . . ; :. ' . . . . . . . . . . . . . . . . . . 7.1.1 Using the NMFS and the NHIS to Estimate Mortality Rates .... 7.1.2 The Estimation of Relative Lung Cancer Risk Associated With Work- place ETS Exposure Using Meta-Analysis . . . . . . . . . . . . . . 7.2 Results of a Risk Assessment for ETS Exposure in the Workplace ..... 29 29 30 31 8 What Can Validly Be Done to Estimate Lifetime Heart Disease Mortality Risks Associated With Workplace ETS Exposure? 34 9 Discussion 34 ~ 0 ~ ~ I

I I I I I ~ I I I I ~ I I List of Tables I Lifetime Occupational Risk for Non-Smoking Workers Exposed to ETS•in the Workplace - OSHA Estimates (Cases per 1000 workers at risk) ..... 14 '2 Percentage of Employed Non-Smokers Aged 20 to 64 by Various Confounding Variables for Persons With and Without Workplace ETS Exposure .... 17 3 Reported Relative Lung Cancer Risks of Workplace ETS Exposure .... 21 4 Lifetime Risk - Number of Lung Cancer Deaths per 1000 Workplace Exposed Non-Smokers Based on NMFS/NHIS Employed Non-Smoker Mortality Rates 33 List of Figures I Reported Relative Lung Cancer. Risks and 95% Confidence Intervals Asso- ciated N-Vith Workplace ETS Exposure . . . . . . . . . . . . . . . . . . . . 23 2 Reported Relative Lung Cancer Risks and 95% Confidence Intervals Asso- ciated ~Vith ~-~Iorkplace ETS Exposure. Studies Reporting on US Data .. 23

Abbreviations I I I I I I I ii CPS Cancer Prevention Survey EPA Environmental Protection Agency .............. . . ........ ,. ~ _. ETS Environmental tobacco smoke NHIS National Health Interview Survey NMFS National Mortality Followback Survey OSHA Occupational Safety and Health Administration RR Relative risk 3

1 Executive Summary I I I I In response to a recent request for information on indoor air quality problems the US Oc- cupational Health and Safety Administration (OSHA) has proposed a standard addressing indoor air quality in general, and especially environmental tobacco smoke (ETS), in in- door work environments. As justification for their standard, OSHA relies on a quantitative risk assessment used to provide estimates of lifetime risk of lung cancer and heart disease associated with workplace exposure to ETS. However, there are a number of concerns regarding the OSHA risk assessment. . The form of the underlying mathematical model used in the risk assessment is in- appropriate. For example, no account is taken for differences in race, age, and sex between those exposed to ETS, and those not so exposed. Workp ace exposure to ETS is assumed to be the sole cause of any difference in mortality rates between the exposed and unexposed, . OSHA was highly selective in choosing what data values to use in their risk assess- ment. ment. For example, OSHA used only the Fontham et al (6] study to estimate relative lung cancer risk associated with ETS exposure. In fact several studies meet OSHA's acceptance criteria_and provide alternative estimates of the relative risk. s Many data values required as input to the OSHA risk assessment model are simply not known at this time. When such values are required, known, but possibly inappropriate values were substituted. For example, where an estimate of relative heart disease 4 I I

risk associated with workplace ETS exposure is required, an estimate based on ETS exposure within the home is substituted. Since ETS exposure within the home is highly correlated with socioeconomic status and with paraoccupational exposure of the home members, such a substitution may be inappropriate. I I t I I 1 I I We present an alternative risk assessment, avoiding the above problems with the OSHA risk assessment. Data from the National Mortality Followback Survey and the National Health Interview Survey were used to obtain nationally representative never-smoker lung cancer rates. Meta-analysis was employed to make use of all available data regarding lung cancer risk associated with workplace ETS exposure. To the extent that these data allow, partial control for confounding from age, race and sex was performed. The results of this risk analysis show no elevated lifetime lung cancer risk associated with workplace ETS exposure. Insufficient dataa exists to perform a similar analysis for heart disease. ~ ~ 5 W 4 ~ . ~

I ~ I ~ I I I I I I 2 Introduction In response to a recent request for information on indoor air quality problems the US Oc- cupational Health and Safety Administration (OSHA) has proposed a standard addressing indoor air'quality in indoor work environments. The provisions of the proposed standard will apply to all indoor "nonindustrial work environments". A large proportion of the OSHA standard deals with workers' exposure to environmental tobacco smoke (ETS). As justification for their standard, OSHA relies on a quantitative risk assessment used to pro- vide estimates of lifetime risk of lung cancer and heart disease associated with workplace exposure to ETS (cf Section IV. of the OSHA report [20, pp.15992-16000]). Our critical review will address three issues: 1. Just how did OSHA proceed in estimating risks associated with workplace ETS ex- posure? Which model did they use? How was adjustment made for key variables that were either included or omitted? The purpose of this first discussion is to simply clarify the method, the mathematical model and the data used by OSHA to arrive at their risk estimate. 2. Is the risk analysis performed by OSHA valid? If not, why is it not valid? 3. How could presently available data be used to assess the risk of ETS in the workplace? 6

I I i 3 Methods 3.1. Notation We use the following notation, consistent with that developed in [24]. Quantities of interest I include the following: • P - persons at risk • D - deaths occuring among the population at risk • R - annual mortality rate • RR - relative risk of workplace ETS exposure . Q - proportion of persons exposed to ETS in the workplace . ED - excess deaths due to workplace ETS exposure . AR - attributable risk due to workplace ETS exposure . LAR - lifetime attributable risk due to to workplace ETS exposure These quantities may be indexed by the following subscripts. 9 c - cause of death (Lung Cancer,Heart Disease) • s-sex s r - race . a - age . k - smoking status (k = non-smoker) 9 e - employment status (employed,not employed) s x - workplace ETS exposure status (a = not exposed) 7 I

The absence of a subscript indicates that the corresponding variable is ignored in com- I I I 1 puting the quantity. Thus for example, R,,,.ak,s refers to the annual mortality rate for cause c ainong employed non-smokers of sex s, race r, age a, who are exposed to ETS at their workplace. The above quantities are unknown population parameters. They are estimated from various data sources, including census data, special purpose surveys and epidemiological studies. An estimator for a population parameter is indicated by putting a" over the parameter, as in k,,.axes. 3.2 Outline of the Mathematical Model The parameter of major interest is the lifetime attributable risk due to workplace ETS exposure. In turn, this quantity depends on the number of deaths which may be ascribed to workplace ETS exposure. The number of deaths from cause c due to workplace ETS exposure for persons of sex s, race r, age a, smoking group k, and employment status e is calculated using the "subtractive method" (24). EDearaker = Dcsrake - ParakeRc:rake.e Psrake (• icarake - Rearaket) (1) Thus, the number of excess deaths due to exposure to ETS is obtained by subtracting from the number of observed deaths (DeJrake) the number of deaths that would have occurred 8

I I I I I ~ ~ I I I had the persons at risk been subject to the mortality rate of those persons not exposed to ETS in the workplace (PsrakeResraxef). No data exist for estimating the absolute mortality risk among those not exposed to ETS in the workplace (Resraket). However, the need for these data can be eliminated, since P Dcsrake Rcsrake - P.rake Desraker Psraker Desrakez Psrake= Psraker Psrake PsrakeY Psrake = RcsrakexQsraker + Rcsrake3(1 - Qsraker) so that Thus Rcsrake RRcsral:exQsraker + (1 - Qsraker) This equation expresses the mortality rate among those not exposed to ETS in terms of the mortality rate of the population at risk (Resrake), the relative risk of exposure to ETS (RReJraker) and the proportion of the population at risk exposed to ETS (Qsrakes)• Substituting this equation into equation I gives the formula Qsraker (RRcsrakex - ~ ~ %Dcsrnket = ~esrake [/lsrakea (RResraker - 1) + 1 Rcsrnke _ RRcarakerQsral:er + (1 - Qsrakes) RcsraL'eS Rcsrakei ~--- - I