Table 3

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 LHCButadieneStyrene
Lymphoid leukaemia
Quartile† N RR 95% CI N RR 95% CI
 Unexposed131.0ref101.0ref
 190.720.29 to 1.78100.750.29 to 1.98
 2100.850.34 to 2.14111.250.47 to 3.33
 3102.611.02 to 6.67101.140.41 to 3.16
 4101.950.76 to 5.03111.780.64 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=521.63×10−3((0.03 to 3.23)×10−3), p=0.046, AIC=936, N=52
Exposed person-time: β(95% CI), trend p value, AIC, N4.78×10−4((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, N15.40×10−4((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
 Unexposed141.0ref111.0ref
 1131.160.53 to 2.56141.270.54 to 2.98
 2141.960.88 to 4.38141.370.56 to 3.31
 3131.470.64 to 3.40141.850.74 to 4.60
 4131.720.73 to 4.07141.810.71 to 4.64
Trend
All person-time: β(95% CI), trend p value, AIC, N1.09×10−4((−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, N0.63×10−4((−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
 Unexposed91.0ref61.0ref
 181.280.47 to 3.4881.550.49 to 4.91
 282.040.73 to 5.7092.260.70 to 7.31
 381.850.64 to 5.3694.611.37 to 15.56
 481.900.63 to 5.7392.420.69 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
 Unexposed341.0ref241.0ref
 1190.900.50 to 1.61210.810.42 to 1.55
 2190.570.31 to 1.04221.020.53 to 1.98
 3190.940.50 to 1.75211.110.56 to 2.21
 4191.330.71 to 2.49221.550.77 to 3.09
Trend
All person-time: β(95% CI), trend p value, AIC, N0.26×10−4((−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, N1.55×10−4((−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, N14.80×10−4((5.68 to 23.99)×10−4), p=0.002, AIC=1286, N=754.20×10−3((−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
 Unexposed201.0ref171.0ref
 1100.610.27 to 1.35100.960.42 to 2.20
 2100.740.32 to 1.71110.610.26 to 1.40
 3100.690.29 to 1.60110.440.19 to 1.04
 4101.010.43 to 2.42110.840.34 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=600.15×10−3((−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=400.31×10−3((−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, N5.83×10−4((−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
 Unexposed651.0ref501.0ref
 1370.750.49 to 1.15410.890.57 to 1.40
 2370.700.45 to 1.08400.830.52 to 1.32
 3370.940.60 to 1.49410.850.53 to 1.38
 4371.390.88 to 2.20411.180.72 to 1.93
Trend
All person-time: β(95% CI), trend p value, AIC, N1.15×10−4((−0.75 to 3.05)×10−4), p=0.237, AIC=3785, N=2135.65×10−4((−4.74 to 16.03)×10−4), p=0.287, AIC=3785, N=213
Exposed person-time: β(95% CI), trend p value, AIC, N1.95×10−4((−0.11 to 4.02)×10−4), p=0.064, AIC=2517, N=1485.51×10−4((−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, N11.00×10−4((4.23 to 17.82)×10−4), p=0.002, AIC=2380, N=14117.00×10−4((−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.