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The attributable risk among the exposed is then given by I ARcarakex _ EDesrakes1Psrake = Rurake ~n~ [Qsrakex (Ri ~esrakes ~ 1) + 1 (2) I I I I I I I t I ARc,rake= is interpreted as the annual probability that a persons of sex s, race r, age a, smoking status k and employment status e will die from cause c as a result of workplace ETS exposure. Over the course of a working lifetime (ages 20-65) the probability of not dying due to cause c as the result of ETS exposure is jIQS 20(1 - ARc,rakex). Thus the (working) lifetime occupational risk is given by 65 LARcsrxex = 1 - 11 (1 - AR,ake=) a_zo (3) ~ ~ ~ Gn 10 '~ ~ IA to

I I I I I I I I I I ~ I I 4 OSHA's Risk Estimates OSHA did not consider differences in sex, race, age and smoking status between the exposed and unexposed groups; accordingly the corresponding subscripts do not appear in the formulas they used. In particular, the attributable risk among the exposed then becomes: AR{AEr = ED~k-.z/PLe = R~~~ ~Q~s (RR~R=c 1) + 1~ (4) Since this quantity ignores age, the lifetime occupational risk is obtained from equation 3 as LARrx= = I - (1 - AR.ck= )4s 4.1 Data Sources (5) The population parameters used in equation 3 are in general unknown, and must be esti- mated from a variety of sources. Specifically, there are three sets of parameters that must be estimated. • Ql.,s The proportion of all employed non-smokers who are exposed to ETS in the workplace. . RR~~,.., The relative cause. c risk of workplace ETS exposure among employed non- smokers.

+ R~k., The cause c mortality rates among employed non-smokers. 4.1.1 The Proportion of Employed Non-Smokers With Workplace ETS Expo- sure I I I I ~ I The OSHA risk model assumes a constant proportion of employed non-smokers are exposed to ETS in the workplace, regardless of sex, race, age or non-srnoking status (ie never smoker or former smoker). They offer two estimates of this constant proportion: • 0.1881 - from the 1991 National Health Interview Survey (NHIS) Health Promotion and Disease Prevention Supplement [7]. • 0.4867 - from Cummings et al (3]. 4.1.2 The Relative Risk of Workplace ETS Exposure Among Non-Smokers OSHA restricts its. risk assessment to two causes of death: lung cancer and heart disease. The OSHA risk model tacitly assumes the relative risk comparing employed non-smokers with workplace exposure to ETS to employed non-smokers with no such exposure is inde- pendent of sex, race and age differences in the groups being compared. For lung cancer, OSHA uses an estimate of RR(Iu„9)I-,= = 1.34 for all sexes, races, and ages, based on Fontliam et al [6]. For heart disease, OSHA uses an estimate of RRlhenrtliiu = 1.28 for all sexes, races, and ~ ages, based on Helsing et al [10]. ~ ~ 12 CZ) W ~ ~

4.1.3 The Mortality Rates of Employed Non-Smokers I I I I I I I I I I I I I As with the relative risk parameter, the OSHA risk model assumes that the annual mortality rate of lung cancer and heart disease for employed non-smokers is independent of sex, race and age. For lung cancer, OSHA uses 0.121 deaths per 1000 non-smokers, as estimated from the Cancer Prevention Survey (CPS) conducted by the American Cancer Society. For heart disease, the Framingham study provides an estimate of 3 deaths per 1000 persons aged 35 to 64. ~ ~ 13 on tU ~ I

5 Result of OSHA's Risks Assessment I I I I I I t ~ I In the OSHA model, each estimate of lifetime risk depends upon estimates of three pa- rameters: the proportion of non-smoking workers exposed to ETS in the workplace, the niortality rate of employed non-smokers and the relative risk of non-smoking workers com- pared to non-smoking workers with no such exposure. For both lung cancer and heart disease two estimates of the proportion of non-smoking workers exposed to ETS in the workplace are used: the "low proportion exposed" estimate (0.1881) from the NHIS and the "high proportion exposed" estimate (0.4867) from Cummings et al [3]. For lung cancer, the mortality rate estimate of .121 deaths per 1000 persons, from the CPS and the relative risk estimate of 1.34 from Fontham et al [6] are used. For heart disease, the mortality rate of 3 deaths per 1000 persons from the Franiingham study and the relative risk estimate of 1.28 based on Helsing et al [10] are used. Table 1: Lifetime Occupational.. Risk for Non-Smoking Workers Exposed to ETS in the Workplace - OSHA Estimates (Cases per 1000 workers at risk) Proportion Exposed Lung Cancer Heart Disease Low (0.1881) 0.4 7 High (0.4867) 1.0 16 The results of OSHA's risk assessment, in terms of lifetime risk (number of deaths per thousand exposed non-smoking workers) are given in Table 1. For the "low proportion" of exposed non-smokers oS.HA estimates a lifetime lung cancer risk per thousand of 0.4 for lung cancer, 7.0 for heart disease. For the "high proportion" of exposed non-smokers, the 14

a I U I I I I I I ~ I I I I lifetime risk estimates are 1.0 for lung cancer and 16.0 for heart disease. 6 An Evaluation of OSHA's Procedure , 6.1 The Mathematical Model The subtractive method appears to be a simple ineans of assessing the impact of expo- sure to an agent. However, this apparent simplicity belies two very strong, implicit and untestable assumptions that must be made to ensure the numbers produced by the model are meaningful. Specifically, the subtractive method assumes that . Persons with and without workplace ETS exposure do not differ with respect to confounding risk factors that are not explicitly controlled for. . Workplace exposure to ETS is the cause of the difference in mortality rates between the exposed and unexposed. In the current risk assessment, this amounts to assuming that persons with and without workplace ETS exposure differ only with respect to that exposure and do not differ with regard to other confounding variables, including for example, sex, race, age, non-smoking status (never vs. former smoker), spousal ETS exposure, nutritional habits, occupation and income. This assumption is inherent in the model used by OSHA and cannot be eliminated ~ or avoided without adding appropriate parameters to the model. ~ r .. GID 15 ~ ~ ~ I

The OSHA risk assessment lumps together males and females, whites and blacks and all age groups. Failing to adjust for age alone should be cause for concern, since mortality rates are so strongly age-dependent. While OSHA recognizes the important differences among these exposed groups I i I I I I I I ; However, the extent of absorption, distribution, retention and meta o ism o [ETS] in the body depends upon various physiological and pharmacokinetic pa- rameters that are influenced by gender,race,age and smoking habits of the ex- posed individuals. These parameters and others may result in differences in susceptibilty among ezposed subpopulations. [20, page 15974] OSHA's risk assessment does not. Failing to control for differences in confounding variables between the exposed and unexposed groups does not impede OSHA's ability to perform calculations, but it does raise serious questions about the validity and the interpretation of the results of such calculations. Data from Cummings et al [3] referenced in the OSHA report itself [20, Table IV-9, page 159951 may be used to illustrate this point. The Cummings data show that among employed males with workplace ETS exposure, 37.5% are also exposed at home. In contrast, among employed males without workplace ETS exposure, only 30.7% are exposed at home. Thus the probability of being exposed to ETS at home is 22% greater for employed males with workplace ETS exposure than for employed males not exposed to ETS in the workplace. The result of the simplifying assumption would be to overestimate whatever effects may be associated with ETS exposure. 16 I

I I I I I I I I I I Data from on the 1991 NHIS Health Promotion and Disease Prevention Supplement further show the differences in confounding variables between persons exposed to ETS at the workplace and those not so exposed. Table 2 shows the percentage of employed non-smokers aged 20 to 64 by various confounding variables for those persons with and r without workplace ETS exposure. Thus for example, 49% of non-smokers with workplace ETS exposure are females, whereas 57% of non-smokers without workplace ETS are females. The table shows that non-sivokers exposed to ETS at the workplace contain relatively more younger persons and persons exposed to ETS at home and contain relatively fewer females, persons with professional or managerial jobs, persons with family income at least $50,000, college graduates and never smokers. Again, failure to control for these confounders would result in overestimation of any risk associated with workplace ETS exposure. Table 2: Percentage of Employed Non-Smokers Aged 20 to 64 by Various Confounding Variables for Persons With and Without Workplace ETS Exposure Confounder . Workplace ETS No Workplace ETS Female 49% 57% Age 20 to 35 45% 40% Home ETS Exposure 22% 15% Professional/Managerial 36% 48% $50,000 Family Income 33% 39% College Grad 30% 46% Never Smoker 66% 72% I N ~ ~ I ~ 17 ~ I ~ Q~

6.2 How Appropriate Are the Population Parameter Estimates I I I I I I I I I I I I I I Utilized in OSHA's Mathematical Model? 6.2.1 The Proportion of Employed Non-Smokers Exposed to ETS in the Work- 0 place OSHA's risk model assumes a constant proportion of employed non-smokers are exposed to ETS in the workplace irrespective of their sex, race, age or non-smoking status (ie never or former smokers). Two estimates for that proportion are used. One of them (.1881) is based on the 1991 NHIS, while the other (.4867) is derived from Cummings et al. The US National Center for Health Statistics has for over thirty years conducted an annual large-scale survey known as the National Health Interview Survey (NHIS). This survey is based on a probability sample of the civilian, noninstitutionalized population and is designed to provide accurate and nationally representative estimates of a large number of health related variables. More than 40,000 persons were interviewed in the 1991 NHIS Health Promotion and Disease Prevention Supplement. Cummings et al [3] drew their sample from persons who attended the Roswell Park Memorial Institute Cancer Screening Clinic in New York for a free cancer checkup during 1986. Following the checkup, persons were asked if they would participate in a study on ETS which required them to make certain observations during four days and participate in a number of interviews regarding their notes.. About 30% of the clinic attendees declined to participate in the ETS study. 18 I

Although OSHA does carry out its calculations using both the NHIS and the Cum- I I I I I I I I I I I I mings et al estimates, in the end it is only the Cummings et al estimate is given any . credence. It is difficult to see how these two estimates can be equated. One estimate is based on a 40,000 strong probability sample of the US population; the other is based on a group of individuals who were sufficiently concerned with their health to attend a nearby screening clinic, take a cancer checkup, and who furthermore agreed to become subjects in a study of ETS. In esssence, OSHA rejects the findings by NHIS and gives greater credence to the results of a small self-selected sample of volunteers. Furthermore, there is the question of consistency of the NHIS and the Cummings es- timates. Whereas the Cummings estimate is an estimate of the proportion of employed non-smokers exposed to ETS at work but not at home, the NHIS estimate is an estimate of the proportion of employed non-smokers with workplace exposure, regardless of their ETS exposure_at home. The estimate of.the proportion of employed non-smokers with workplace exposure regardless of their ETS exposure at home based on the Cummings data is 0.7789, or over 4 times as high as the tTHIS estimate. It seems clear that the two estimates cannot be measuring the same quantity. The acceptance of Cummings et al as a serious estimate of the proportion of employed non-smokers exposed to ETS is not unimportant. Estimates of the lifetime occupational risk attributable to workplace ETS exposure depend on the number of non-smokers so ex- posed. The larger the estimated proportion, the larger the calculated lifetime occupational risk. The use of the Cummings et al result is, from a statistical viewpoint, simply not an 19 I