Sir,
We appreciate the thoughtful comments by Rylander and Jacobs (2014) on our paper (Checkoway et al, 2014). The absence of an inverse exposure–response relation for endotoxin and lung cancer in the extended follow-up was somewhat unexpected in view of the reported consistent findings from numerous prior studies, including our initial follow-up of the Shanghai textile worker cohort (Astrakianakis et al, 2007). Although neither the modest excess relative risks observed nor the exposure–response trend for exposures >15 years since first exposure (Table 3) were statistically significant, the findings are somewhat suggestive of a possible late pro-carcinogenic effect. We do not believe that our observations on endotoxin exposure and lung cancer risk necessarily challenge a well-established association. Instead, we would argue that the exposure–response association may change over time owing to complex, yet poorly understood, underlying mechanisms. We are also not the first to report that an inverse association between endotoxin and lung cancer risk may be time varying, diminishing over time (Mastrangelo et al, 2005).
We have acknowledged the absence of data on risk factors other than active smoking, such as indoor air pollution from cooking fuels and diet. However, it is highly unlikely that either indoor air pollution or diet was correlated with endotoxin exposure in this cohort, and thus were probably not important confounders. Socio-economic status was relatively homogenous in the cohort, and also was unlikely to have been a confounder. Our exposure assessment for endotoxin (Astrakianakis et al, 2006) did take into account temporal changes in exposure levels during the cohort’s relevant work experience, to the extent that available historical data permitted. Endotoxin is a highly variable exposure, and as we noted in the paper, some exposure misclassification was inevitable.
We encourage analyses that consider temporal patterns of association in other endotoxin-exposed study populations, which can provide valuable insights into disease aetiology and pathogenesis.
References
Astrakianakis G, Seixas NS, Camp JE, Christiani DC, Feng Z, Thomas DB, Checkoway H (2006) Modeling, estimation and validation of cotton dust and endotoxin exposures in Chinese textile operations. Ann Occup Hyg 50 (6): 573–582.
Astrakianakis G, Seixas NS, Ray R, Camp JE, Gao DL, Feng Z, Li W, Wernli KJ, Fitzgibbons ED, Thomas DB, Checkoway H (2007) Lung cancer risk among female textile workers exposed to endotoxin. J Natl Cancer Inst 99 (5): 357–364.
Checkoway H, Lundin JI, Costello S, Ray R, Li W, Eisen EA, Astrakinakis G, Seixas N, Applebaum K, Gao DL, Thomas DB (2014) Possible Pro-carcinogenic association of endotoxin on lung cancer among Shanghai women textile workers. Brit J Cancer 111 (3): 603–607.
Mastrangelo G, Grange JM, Fadda E, Fedeli U, Buja A, Lange JH (2005) Lung cancer risk: effect of dairy farming and the consequence of removing that occupational exposure. Am J Epidemiol 161 (11): 1037–1046.
Rylander R, Jacobs R (2014) Comment on ‘Possible pro-carcinogenic association of endotoxin on lung cancer among Shanghai women textile workers’. Br J Cancer e-pub ahead of print 20 November 2014; doi:10.1038/bjc.2014.583.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
This work is licensed under the Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/
About this article
Cite this article
Checkoway, H., Lundin, J., Costello, S. et al. Reply to Comment on: ‘Possible pro-carcinogenic association of endotoxin on lung cancer among Shanghai women textile workers’. Br J Cancer 112, 1840–1841 (2015). https://doi.org/10.1038/bjc.2014.584
Published:
Issue Date:
DOI: https://doi.org/10.1038/bjc.2014.584
This article is cited by
-
Textile industry and occupational cancer
Journal of Occupational Medicine and Toxicology (2016)