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Objectives: Chronic bronchitis (CB) is an important chronic obstructive pulmonary disease (COPD)-related phenotype, with distinct clinical features and prognostic implications. Occupational exposures have been previously associated with increased risk of CB but few studies have examined this association prospectively using objective exposure assessment. We examined the effect of occupational exposures on CB incidence in the European Community Respiratory Health Survey., Methods: Population samples aged 20-44 were randomly selected in 1991-1993, and followed up twice over 20 years. Participants without chronic cough or phlegm at baseline were analysed. Coded job histories during follow-up were linked to the ALOHA Job Exposure Matrix, generating occupational exposure estimates to 12 categories of chemical agents. Their association with CB incidence over both follow-ups was examined with Poisson models using generalised estimating equations., Results: 8794 participants fulfilled the inclusion criteria, contributing 13 185 observations. Only participants exposed to metals had a higher incidence of CB (relative risk (RR) 1.70, 95% CI 1.16 to 2.50) compared with non-exposed to metals. Mineral dust exposure increased the incidence of chronic phlegm (RR 1.72, 95% CI 1.43 to 2.06). Incidence of chronic phlegm was increased in men exposed to gases/fumes and to solvents and in women exposed to pesticides., Conclusions: Occupational exposures are associated with chronic phlegm and CB, and the evidence is strongest for metals and mineral dust exposure. The observed differences between men and women warrant further investigation., Competing Interests: Competing interests: DJ reports grants from European Commission during the conduct of the study. VS reports grants from the Wood Dust Foundation (Project No 444508795) during the conduct of the study. IP reports non-financial support and other from Novartis, personal fees and other from Astra Zeneca, non-financial support and other from Chiesi, outside the submitted work. PD reports personal fees from ALK, Stallergènes Greer, Chiesi, Thermo Fisher Scientific, Ménarini, Bausch&Lomb and Mylan, outside the submitted work. RJ reports grants from Estonian Research Council (personal research grant number 562) during the conduct of the study, personal fees and non-financial support from GSK, personal fees from Novartis and Boehringer, outside the submitted work., (© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

Standard Reference Material 3280 Multivitamin/ Multielement Tablets was issued by the National Institute of Standards and Technology in 2009, and has certified and reference mass fraction values for 13 vitamins, 26 elements, and two carotenoids. Elements were measured using two or more analytical methods at NIST with additional data contributed by collaborating laboratories. This reference material is expected to serve a dual purpose: to provide quality assurance in support of a database of dietary supplement products and to provide a means for analysts, dietary supplement manufacturers, and researchers to assess the appropriateness and validity of their analytical methods and the accuracy of their results.