TABLE 4.
Additive scale interactions between blood dibromochloromethane (DBCM) and brominated trihalomethanes (Br-THMs; sum of bromodichloromethane, dibromochloromethane and tribromomethane (bromoform)) concentrations and tobacco smoke exposure and the risk of asthma#
| Blood THM | Tobacco smoke exposure ¶ | Ever asthma | Current asthma | ||
| n | OR (95% CI) | n | OR (95% CI) | ||
| DBCM | |||||
| Low DBCM (<75th) | No | 1444 | 1.00 (reference) | 1292 | 1.00 (reference) |
| Yes | 289 | 1.20 (0.85–1.70) | 259 | 1.44 (0.90–2.31) | |
| High DBCM (≥75th) | No | 499 | 0.98 (0.73–1.31) | 457 | 1.05 (0.70–1.59) |
| Yes | 77 | 3.04 (1.80–5.13) | 61 | 3.51 (1.73–7.12) | |
| RERI (95% CI) | 1.87 (0.30–3.43)* | 2.01 (−0.42–4.44) | |||
| Br-THMs | |||||
| Low Br-THMs (<50th) | No | 817 | 1.00 (reference) | 715 | 1.00 (reference) |
| Yes | 166 | 1.08 (0.69–1.69) | 145 | 1.15 (0.59–2.27) | |
| High Br-THMs (≥50th) | No | 1075 | 0.81 (0.63–1.04) | 990 | 1.11 (0.77–1.59) |
| Yes | 195 | 1.67 (1.13–2.48) | 170 | 2.59 (1.52–4.39) | |
| RERI (95% CI) | 0.78 (0.07–1.49)* | 1.32 (0.01–2.64)* | |||
RERI: relative excess risk due to interaction. #: all models were adjusted for age, sex, race/ethnicity, body mass index z-score, family income to poverty ratio, family history of asthma, swimming pool/hot tub/steam room use within 72 h and survey cycle; ¶: participants were considered exposed to tobacco smoke if their serum cotinine concentrations were >10 ng·mL−1 or they had self-reported consumption of tobacco or nicotine products in the past 5 days. *: p<0.05.