Correction to: BMC Public Health 12, 204 (2012)

https://doi.org/10.1186/1471-2458-12-204

This article [1] has been corrected to acknowledge that Figs. 1 and 2 have been reproduced with permission of the© ERS 2021: European Respiratory Journal Feb 2010, 35 (2) 279–286; DOI: 10.1183/09031936.00027509