Study design and participants
We conducted a descriptive cross-sectional study among
workers of the Hamburg sanitation department. The
study was part of a broader occupational and ergonomic
field study which assessed the working conditions and
job strain of municipal waste collectors with qualitative
interviews, real-life observation and objective strain
measurements (e.g. mobile spiroergometry) [13]. For the
study, waste collectors were recruited by the human resources
department of the municipal waste collection
services of the City of Hamburg with the involvement of
the safety engineer and collection tour planners. Participation
in the field study was voluntary and rewarded
with two days off. The sampling method was predefined
by the ergonomic study and aimed at representing the
broad spectrum of working conditions in the collection
tours (i.e. areas with low and high population density,
areas with frequent architectonic barriers, predominant
type and size of container, etc.) and the two main work
groups (street waste collectors and household waste collectors).
The sample size was also determined by the
ergonomic field study. The final study group consisted
of 65 persons (62 male and 3 female) who were all active
(i.e. not on sick leave) at the time of data collection (between
January and August 2013). The majority of participants
(71 %) were working in the household waste
collection service.