Exposure-response analyses of butadiene or styrene ppm-years and other lymphohaematopoietic cancers (LHCs): number (N) of cases, adjusted rate ratio (RR) with 95% CI by exposure quartile, beta-coefficient (β) with 95% CI and trend p value
| Model*, form of LHC | Butadiene | Styrene | ||||
| Lymphoid leukaemia | ||||||
| Quartile† | N | RR | 95% CI | N | RR | 95% CI |
| Unexposed | 13 | 1.0 | ref | 10 | 1.0 | ref |
| 1 | 9 | 0.72 | 0.29 to 1.78 | 10 | 0.75 | 0.29 to 1.98 |
| 2 | 10 | 0.85 | 0.34 to 2.14 | 11 | 1.25 | 0.47 to 3.33 |
| 3 | 10 | 2.61 | 1.02 to 6.67 | 10 | 1.14 | 0.41 to 3.16 |
| 4 | 10 | 1.95 | 0.76 to 5.03 | 11 | 1.78 | 0.64 to 4.91 |
| Trend | ||||||
| All person-time: β(95% CI), trend p value, AIC, N‡ | 3.81×10−4((1.05 to 6.58)×10−4), p=0.007, AIC=933, N=52 | 1.63×10−3((0.03 to 3.23)×10−3), p=0.046, AIC=936, N=52 | ||||
| Exposed person-time: β(95% CI), trend p value, AIC, N | 4.78×10−4((1.34 to 8.23)×10−4), p=0.007, AIC=664, N=39§ | 1.24×10−3((−0.43 to 2.91)×10−3), p=0.146, AIC=727, N=42§ | ||||
| Exposed person-time ≤95th percentile: β(95% CI), trend p value, AIC, N | 15.40×10−4((4.19 to 26.53)×10−4), p=0.007, AIC=625, N=37§ | 3.33×10−3((−4.81 to 11.47)×10−3), p=0.422, AIC=689, N=40§ | ||||
| Myeloid leukaemia | ||||||
| Quartile | N | RR | 95% CI | N | RR | 95% CI |
| Unexposed | 14 | 1.0 | ref | 11 | 1.0 | ref |
| 1 | 13 | 1.16 | 0.53 to 2.56 | 14 | 1.27 | 0.54 to 2.98 |
| 2 | 14 | 1.96 | 0.88 to 4.38 | 14 | 1.37 | 0.56 to 3.31 |
| 3 | 13 | 1.47 | 0.64 to 3.40 | 14 | 1.85 | 0.74 to 4.60 |
| 4 | 13 | 1.72 | 0.73 to 4.07 | 14 | 1.81 | 0.71 to 4.64 |
| Trend | ||||||
| All person-time: β(95% CI), trend p value, AIC, N | 1.09×10−4((−3.01 to 5.18)×10−4), p=0.602, AIC=1235, N=67 | −2.36×10−4((−32.20 to 27.48)×10−4), p=0.877, AIC=1235, N=67 | ||||
| Exposed person-time: β(95% CI), trend p value, AIC, N | 0.63×10−4((−3.89 to 5.15)×10−4), p=0.784, AIC=941, N=53¶ | −3.77×10−4((−35.71 to 28.17)×10−4), p=0.817, AIC=1006, N=56 | ||||
| Exposed person-time ≤95th percentile: β(95% CI), trend p value, AIC, N | −0.16×10−4((−14.68 to 14.37)×10−4), p=0.983, AIC=880, N=50¶ | 29.50×10−4((−49.06 to 108.13)×10−4), p=0.461, AIC=963, N=54 | ||||
| Acute myeloid leukaemia | ||||||
| Quartile | N | RR | 95% CI | N | RR | 95% CI |
| Unexposed | 9 | 1.0 | ref | 6 | 1.0 | ref |
| 1 | 8 | 1.28 | 0.47 to 3.48 | 8 | 1.55 | 0.49 to 4.91 |
| 2 | 8 | 2.04 | 0.73 to 5.70 | 9 | 2.26 | 0.70 to 7.31 |
| 3 | 8 | 1.85 | 0.64 to 5.36 | 9 | 4.61 | 1.37 to 15.56 |
| 4 | 8 | 1.90 | 0.63 to 5.73 | 9 | 2.42 | 0.69 to 8.54 |
| Trend | ||||||
| All person-time: β(95% CI), trend p value, AIC, N | −1.08×10−4((−9.12 to 6.97)×10−4), p=0.793, AIC=746, N=41 | −6.23×10−4((−51.03 to 38.56)×10−4), p=0.785, AIC=746, N=41 | ||||
| Exposed person-time: β(95% CI), trend p value, AIC, N | −2.27×10−4((−12.25 to 7.70)×10−4), p=0.655, AIC=561, N=32¶ | −1.13×10−3((−6.48 to 4.22) x10−3), p=0.679, AIC=623, N=35 | ||||
| Exposed person-time ≤95th percentile: β(95% CI), trend p value, AIC, N | −1.34×10−3((−3.93 to 1.25)×10−3), p=0.310, AIC=540, N=31¶ | −3.02×10−3((−15.36 to 9.32)×10−3), p=0.631, AIC=602, N=34 | ||||
| Non-Hodgkin’s lymphoma | ||||||
| Quartile | N | RR | 95% CI | N | RR | 95% CI |
| Unexposed | 34 | 1.0 | ref | 24 | 1.0 | ref |
| 1 | 19 | 0.90 | 0.50 to 1.61 | 21 | 0.81 | 0.42 to 1.55 |
| 2 | 19 | 0.57 | 0.31 to 1.04 | 22 | 1.02 | 0.53 to 1.98 |
| 3 | 19 | 0.94 | 0.50 to 1.75 | 21 | 1.11 | 0.56 to 2.21 |
| 4 | 19 | 1.33 | 0.71 to 2.49 | 22 | 1.55 | 0.77 to 3.09 |
| Trend | ||||||
| All person-time: β(95% CI), trend p value, AIC, N | 0.26×10−4((−3.73 to 4.25)×10−4), p=0.898, AIC=1976, N=110 | −0.23×10−3((−2.62 to 2.17)×10−3), p=0.854, AIC=1976, N=110 | ||||
| Exposed person-time: β(95% CI), trend p value, AIC, N | 1.55×10−4((−2.49 to 5.58)×10−4), p=0.452, AIC=1317, N=76 | −0.15×10−3((−2.56 to 2.26)×10−3), p=0.900, AIC=1506, N=86 | ||||
| Exposed person-time ≤95th percentile: β(95% CI), trend p value, AIC, N | 14.80×10−4((5.68 to 23.99)×10−4), p=0.002, AIC=1286, N=75 | 4.20×10−3((−0.73 to 9.13)×10−3), p=0.095, AIC=1462, N=84 | ||||
| Multiple myeloma | ||||||
| Quartile | N | RR | 95% CI | N | RR | 95% CI |
| Unexposed | 20 | 1.0 | ref | 17 | 1.0 | ref |
| 1 | 10 | 0.61 | 0.27 to 1.35 | 10 | 0.96 | 0.42 to 2.20 |
| 2 | 10 | 0.74 | 0.32 to 1.71 | 11 | 0.61 | 0.26 to 1.40 |
| 3 | 10 | 0.69 | 0.29 to 1.60 | 11 | 0.44 | 0.19 to 1.04 |
| 4 | 10 | 1.01 | 0.43 to 2.42 | 11 | 0.84 | 0.34 to 2.08 |
| Trend | ||||||
| All person-time: β(95% CI), trend p value, AIC, N | −0.82×10−4((−5.08 to 3.45)×10−4), p=0.707, AIC=1056, N=60 | 0.15×10−3((−1.55 to 1.85)×10−3), p=0.858, AIC=1056, N=60 | ||||
| Exposed person-time: β(95% CI), trend p value, AIC, N | −0.36×10−4((−4.86 to 4.14)×10−4), p=0.876, AIC=669, N=40 | 0.31×10−3((−1.44 to 2.05)×10−3), p=0.731, AIC=730, N=43 | ||||
| Exposed person-time ≤95th percentile: β(95% CI), trend p value, AIC, N | 5.83×10−4((−7.64 to 19.30)×10−4), p=0.396, AIC=634, N=38 | −1.61×10−3((−9.61 to 6.38)×10−3), p=0.692, AIC=644, N=38 | ||||
| B-cell malignancy | ||||||
| Quartile | N | RR | 95% CI | N | RR | 95% CI |
| Unexposed | 65 | 1.0 | ref | 50 | 1.0 | ref |
| 1 | 37 | 0.75 | 0.49 to 1.15 | 41 | 0.89 | 0.57 to 1.40 |
| 2 | 37 | 0.70 | 0.45 to 1.08 | 40 | 0.83 | 0.52 to 1.32 |
| 3 | 37 | 0.94 | 0.60 to 1.49 | 41 | 0.85 | 0.53 to 1.38 |
| 4 | 37 | 1.39 | 0.88 to 2.20 | 41 | 1.18 | 0.72 to 1.93 |
| Trend | ||||||
| All person-time: β(95% CI), trend p value, AIC, N | 1.15×10−4((−0.75 to 3.05)×10−4), p=0.237, AIC=3785, N=213 | 5.65×10−4((−4.74 to 16.03)×10−4), p=0.287, AIC=3785, N=213 | ||||
| Exposed person-time: β(95% CI), trend p value, AIC, N | 1.95×10−4((−0.11 to 4.02)×10−4), p=0.064, AIC=2517, N=148 | 5.51×10−4((−5.19 to 16.20)×10−4), p=0.313, AIC=2809, N=163 | ||||
| Exposed person-time ≤95th percentile: β(95% CI), trend p value, AIC, N | 11.00×10−4((4.23 to 17.82)×10−4), p=0.002, AIC=2380, N=141 | 17.00×10−4((−21.05 to 55.06)×10−4), p=0.381, AIC=2639, N=154 | ||||
*Models used attained age as of each day of follow-up as the time scale. Covariates were age at hire, year of hire, race, sex, plant and ever hourly status. Models using exposed person-time ≤95th percentile trimmed data above 1144 and 171 ppm-years for butadiene and styrene, respectively, for leukaemias and above 1083 and 213 ppm-years for butadiene and styrene, respectively, for non-Hodgkin’s lymphoma, multiple myeloma and B-cell malignancy.
†Quartile (Q) cutpoints were at the following values of ppm-years: lymphoid leukaemia—(1) butadiene: Q2, 44.73; Q3, 213.43; Q4, 376.31, maximum=7741.41; (2) styrene: Q2, 8.52; Q3, 27.21; Q4, 69.29, maximum=1203.21; myeloid leukaemia—(1) butadiene: Q2, 25.20; Q3, 70.05; Q4, 230.08, maximum=–2009.71; (2) styrene: Q2, 5.21; Q3, 20.71; Q4, 48.25, maximum=340.52; acute myeloid leukaemia—(1) butadiene: Q2, 19.14; Q3, 59.19; Q4, 185.63, maximum=2009.71; (2) styrene: Q2, 5.21; Q3, 19.73; Q4, 34, maximum=340.52; non-Hodgkin’s lymphoma—(1) butadiene: Q2, 17.94; Q3, 117.22; Q4, 334.83, maximum=1495.51 (2) styrene: Q2, 5.97; Q3, 23.61; Q4, 59.67, maximum=231.34; multiple myeloma—(1) butadiene: Q2, 31.42; Q3, 107.78; Q4, 386.04, maximum=2397.73; (2) styrene: Q2, 2.80; Q3, 14.67; Q4, 77.99, maximum=839.61; B-cell malignancy—(1) butadiene: Q2, 27.04; Q3, 124.38; Q4, 370.89, maximum=7741.41; (2) styrene: Q2, 4.63; Q3, 20.74; Q4, 61.70, maximum=1203.21.
‡AIC, Akaike information criterion; N, number of cases included in each model.
§Restricted to ever hourly due to lack of events among never hourly.
¶Restricted to men due to lack of events among women.