Indoor Wood-Burning Stove and Fireplace Use and Breast Cancer in a Prospective Cohort Study

[Emily]

https://ehp.niehs.nih.gov/ehp827/

Environ Health Perspect; DOI:10.1289/EHP827

[h=1]Indoor Wood-Burning Stove and Fireplace Use and Breast Cancer in a Prospective Cohort Study[/h] Alexandra J. White and Dale P. Sandler

• Background: Indoor burning of fuel for heating or cooking releases carcinogens. Little is known about the impact of indoor air pollution from wood-burning stoves or fireplaces on breast cancer risk. Objectives: In a large prospective cohort study, we evaluated the risk of breast cancer in relation to indoor heating and cooking practices. Methods: Sister Study participants (n=50,884) were recruited from 2003?2009. Breast cancer?free women in the United States or Puerto Rico, 35?74 y old, with a sister with breast cancer were eligible. Participants completed questionnaires on indoor heating and cooking practices for both their enrollment and their longest adult residence. Cox regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association between indoor heating/cooking and breast cancer. Results: A total of 2,416 breast cancer cases were diagnosed during follow-up (mean=6.4 y). Having an indoor wood-burning stove/fireplace in the longest adult residence was associated with a higher breast cancer risk [HR=1.11 (95% CI: 1.01, 1.22)]; the risk increased with average frequency of use [≥once/week, HR=1.17 (95% CI: 1.02, 1.34)] (p for trend=0.01). An elevated HR was seen for women burning wood [HR=1.09 (95% CI: 0.98, 1.21)] or natural gas/propane [HR=1.15 (95% CI: 1.00, 1.32)]. No association was observed for burning artificial fire-logs [HR=0.98 (95% CI: 0.85, 1.12)] except among women from western states [HR=1.36 (95% CI: 1.02, 1.81)]. Conclusions: In this prospective study, using an indoor wood-burning stove/fireplace in the longest adult residence at least once a week and burning either wood or natural gas/propane was associated with a modestly higher risk of breast cancer. https://doi.org/10.1289/EHP827

There were 2,416 breast cancers diagnosed during the follow-up period (mean=6.4 y), 1,843 of which were determined to be invasive. Having a wood-burning stove/fireplace in the longest adult residence was associated with slightly increased breast cancer risk [Number of exposed cases (n)=1,500; HR=1.11 (95% CI: 1.01, 1.22)] (Table 2). There was a trend of higher breast cancer risk with increased frequency of use (p=0.01); those who used an indoor wood-burning stove/fireplace at least once a week had the highest HR [n=327; HR=1.17 (95% CI: 1.02, 1.34)] relative to those who did not have a wood-burning stove/fireplace in their longest adult residence. Although the HR for invasive cases did not differ significantly from in situ cases in a direct comparison, the estimate for weekly wood-burning stove/fireplace use was apparent for invasive breast cancer [n=265; HR=1.25 (95% CI: 1.07, 1.46)] but not for DCIS [n=59; HR=0.96 (95% CI: 0.70, 1.31)] (invasive vs. DCIS, p=0.7).

A report from the U.S. EPA suggested that fireplaces in the west were notably larger and thus would produce more emissions (Houck et al. 1998), which may explain, possibly in conjunction with differences in age of home and ventilation, the increase in risk observed for women in the west, if this effect is real.