5.6% (95% CI, 4.1–7.0%) in the NHANES population. The rates among both popula- tions increased with age; however, in all cat- egories, the rates were higher among Libby residents. The rates in Libby went from 7.3% (95% CI, 5.0–9.6%) among 10- to 16-year-olds to 15.3% (95% CI, 10.3– 20.3%) among 23- to 29-year-olds. For the NHANES population, these rates are 2.3% (95% CI, 1.3%–3.4%) and 6.6% (95% CI, 3.2–10.0%), respectively. Also, within each age group, the prevalence of usually having a cough was similar between men and women from Libby; in the NHANES population, the prevalence was generally higher among men. However, the prevalence between the two study populations is not directly comparable because the NHANES questionnaire gives a time frame for having a cough, whereas the ATSDR study simply asked about “having a cough on most days” without specifying the length of time the cough had been preva- lent. In addition, the population may differ in other regards, such as smoking prevalence or exposure to different air pollutants. After adjustment for age, sex, and tobacco exposure, frequently handling vermiculite insulation was positively associated with self- reported cough [odds ratio (OR) = 3.38; 95% CI, 1.56–7.31], shortness of breath (OR = 3.28; 95% CI, 1.63–6.63), and coughing up bloody phlegm (OR = 2.75; 95% CI, 1.07– 7.09)] (Table 2). Usually having a cough was also associated with frequently participating in recreational activities along Rainy Creek Road and frequently heating the vermicu- lite to make it expand/pop. Cough was the only symptom associated with the heating of vermiculite, but frequently participating in recreational activities along Rainy Creek Road was related to shortness of breath (OR = 1.89; 95% CI, 1.12–3.19) in addition to its association with cough. The only respiratory symptom associated with frequently playing at the ball fields near the expansion plant was coughing up bloody phlegm (OR = 2.46; 95% CI, 1.04–5.79). Although some of the point estimates were elevated, none of the activities were clearly associated with self-reported lung disease. We further examined the activities by grouping the number/frequency of activities into four categories: never participating in any of the activities, participating only sometimes in at least one of the activities, participating frequently in one or two of the activities, and participating frequently in at least three of the Respiratory symptoms in Libby, MT activities. We found a positive trend between number/frequency of activity and usually hav- ing a cough. Compared with those who never participated in any of the activities, individu- als who participated in at least one activity sometimes, one or two activities frequently, or at least three activities frequently had ORs of 1.88 (95% CI, 0.71–5.00), 2.00 (95% CI, 0.76–5.28), and 2.93 (95% CI, 0.93–9.25), respectively. We found no association between the number/frequency of activities and short- ness of breath, coughing up bloody phlegm, or having a lung disease. The associations present between specific activities and outcomes are similar to those without adjustment for the smoking variables, but the 95% CIs were more precise and the association between number/ frequency of activities and usually having a cough did not include the when we removed the smoking variables from the mod- els. Controlling for only age and sex, the OR for usually having a cough comparing indi- viduals who reported frequently participating in three or more activities and individuals who reported never participating in any of these activities was 3.62 (95% CI, 1.17–11.16). Handling vermiculite insulation was posi- tively associated with three of four self-reported Table 2. Age-, sex-, and tobacco-smoke exposure–adjusted associations between activities with possible exposure to asbestos-containing vermiculite and self- reported respiratory outcomes among individuals ≤ 18 years of age when the mine closed in Libby, Montana. Exposure Cough Casesa Controlsa (n = 108) (n = 894) ORb (95% CIb) Shortness of breath Casesa Controlsa (n = 145) (n = 857) ORb (95% CIb) Bloody phlegm Casesa Controlsa (n = 59) (n = 944) ORb (95% CIb) Lung disease Casesa Controlsa (n = 51) (n = 952) ORb (95% CIb) Association for all activities with potential for Libby amphibole exposure combined (no./frequency of activitiesc) Never 5 100 1.00 10 95 1.00 5 100 1.00 3 102 1.00 Sometimes 39 367 1.88 (0.71–5.00) 52 354 1.16 (0.55–2.44) 19 387 0.85 (0.31–2.38) 23 383 1.95 (0.57–6.71) 1–2 frequently 51 379 2.00 (0.76–5.28) 70 360 1.27 (0.61–2.63) 29 402 1.09 (0.40–2.98) 21 410 1.51 (0.43–5.24) ≥ 3 frequently 12 47 2.93 (0.93–9.25) 13 46 1.32 (0.51–3.42) 6 53 1.49 (0.41–5.43) 4 55 1.72 (0.36–8.32) Associations with individual activities with potential for Libby amphibole exposure Handled vermiculite insulation Never 69 666 1.00 104 631 1.00 41 695 1.00 37 699 1.00 Sometimes 27 188 1.26 (0.77–2.06) 24 191 0.67 (0.41–1.09) 12 203 0.93 (0.48–1.83) 10 205 0.90 (0.44–1.86) Frequently 11 32 3.38 (1.56–7.31) 15 28 3.28 (1.63–6.63) 6 37 2.75 (1.07–7.09) 4 39 1.85 (0.62–5.54) Participated in recreational activities along Rainy Creek Roadd Never 34 393 1.00 45 382 1.00 21 406 1.00 20 407 1.00 Sometimes 42 379 1.16 (0.70–1.90) 62 360 1.30 (0.84–2.00) 23 399 1.02 (0.55–1.91) 24 398 1.17 (0.63–2.19) Frequently 29 115 1.97 (1.10–3.51) 36 108 1.89 (1.12–3.19) 12 132 1.28 (0.59–2.78) 6 138 0.74 (0.28–1.93) Played at the ball fields near the expansion plant Never 24 235 1.00 33 226 1.00 7 252 1.00 12 247 1.00 Sometimes 38 301 1.03 (0.59–1.82) 50 289 0.92 (0.56–1.52) 21 318 2.15 (0.89–5.19) 18 321 0.99 (0.46–2.12) Frequently 44 356 0.91 (0.52–1.59) 61 339 0.85 (0.52–1.39) 30 371 2.46 (1.04–5.79) 20 381 0.88 (0.42–1.88) Played in or around the vermiculite piles Never 66 648 1.00 91 624 1.00 37 678 1.00 32 683 1.00 Sometimes 24 168 1.14 (0.67–1.93) 36 156 1.25 (0.79–1.96) 12 180 1.05 (0.52–2.10) 10 182 1.07 (0.51–2.25) Frequently 14 65 1.46 (0.74–2.87) 14 64 0.93 (0.48–1.80) 9 70 1.85 (0.82–4.17) 7 72 1.65 (0.68–4.03) Heated the vermiculite to make it expand/pop Never 70 675 1.00 109 636 1.00 44 702 1.00 35 711 1.00 Sometimes 24 181 1.26 (0.75–2.13) 23 182 0.61 (0.36–1.01) 11 194 0.81 (0.40–1.65) 10 195 0.97 (0.46–2.05) Frequently 12 36 2.30 (1.08–4.92) 12 36 1.15 (0.55–2.39) 3 45 0.75 (0.22–2.61) 5 43 1.89 (0.68–5.28) Participated in other activities where contact was made with vermiculite insulation, products, or ores not mentioned Never 65 690 1.00 104 651 1.00 45 711 1.00 39 717 1.00 Sometimes 37 168 2.29 (1.45–3.64) 37 168 1.25 (0.81–1.94) 11 194 0.84 (0.42–1.67) 10 195 0.87 (0.43–1.80) Frequently 4 25 1.52 (0.49–4.73) 2 27 0.36 (0.08–1.62) 1 28 0.52 (0.07–4.00) 1 28 0.57 (0.07–4.39) aNumber of cases and controls do not always sum to total because of missing data on exposure. bAdjusted for age, sex, smoking status, and living/lived with a smoker. c“Never“ means never participating in any of the activities; “Sometimes,”participating only sometimes in any of the activities; “1–2 frequently,” participating frequently in one or two of the activities; “≥ 3 frequently,” participating frequently in three or more of the activities. dRainy Creek Road is the road leading to the mine. Environmental Health Perspectives • volume 118 | number 7 | July 2010 1035