2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
OCCUPATIONAL EXPOSURE TO COLD THERMAL
ENVIRONMENTS: A FIELD STUDY IN PORTUGAL
A. Virgílio M. Oliveira 1* , Adélio R. Gaspar 2 , Divo A. Quintela 2
1 Departamento de Engenharia Mecânica, Instituto Superior de Engenharia de Coimbra, Rua
Pedro Nunes - Quinta da Nora, 3030 – 199 Coimbra, Portugal, http://www.isec.pt
2 Departamento de Engenharia Mecânica, Universidade de Coimbra, Pólo II, 3030 – 201
Coimbra, Portugal, http://www.dem.uc.pt
Contact person: avfmo@mail.isec.pt
INTRODUCTION
During the last decades, the improvement of Occupational Safety and Health (OSH) is giving
rise to updated and improved international and national legislation and to the promotion of
public awareness, education and investigation in OSH. As a consequence, different research
studies are being developed in order to characterise the present working conditions. The
occupational exposure to cold environments is one example and it represents a specific field
of the thermal exposure which is almost unknown in Portugal (Oliveira et al., 2005).
Traditionally, the study of heat stress is more common due to our mild climate, and this may
be the reason why cold stress has not been addressed so far. Therefore, a field study
comprising industrial environments was carried out among activities with cold stress
conditions, namely in the food industry. Fish, meat and milk-food production, conservation
and distribution industrial units, hypermarkets and supermarkets were considered. In addition,
a few industrial units from the pharmaceutical distribution were also included. The present
survey supports a description of the occupational cold exposure in the Portuguese industry
and highlights that the number of people working under such thermal conditions is much
more important than it was initially predicted by the authors.
METHODS
The evaluation of thermal stress level is mainly supported by measurements of the physical
parameters [air and mean radiant temperatures (ta and tr), air velocity (va) and humidity (rh)]
and estimation of the individual parameters [metabolic rate (M) and the thermal insulation of
clothing (Icl)], which are assessed in terms of the Required Clothing Insulation Index, IREQ.
Developed by Holmér (1984) and adopted by ISO as a Technical Report (ISO/TR 11079,
1993), the IREQ index provides a method to assess the thermal stress associated with the
exposure to cold environments. It applies to continuous, intermittent and occasional exposure
either for indoor or outdoor work. Two levels of physiological strain, defined in terms of
mean skin temperature, skin wettedness and change in body heat content are proposed:
IREQneutral and IREQmin. The clothing insulation required to maintain thermal equilibrium
(IREQmin) and thermal comfort (IREQneutral) are calculated by satisfying the equations:
tsk
− tcl
IREQ = (1) M − W − Eres
− Cres
− E = R + C (2)
M −W
− Eres
− Cres
− E
where t sk and t cl are the mean skin temperature and the mean clothing surface temperature
[ºC], M is the metabolic rate, W is the effective mechanical work, Eres, Cres, E, R and C
[W/m
594
2 ] are the heat exchanges by respiratory evaporation and convection, by evaporation, by
radiation and by convection, respectively.
When the resultant clothing insulation of the selected ensemble (Iclr) is less than the calculated
required clothing insulation (IREQ), exposure has to be time-limited to prevent progressive
body cooling. Thus, a duration limited exposure (DLE) is defined in terms of the