Evaluation of heat strain experienced by furnace workers at an iron smelter
Abstract
Background: Any working environment where industrial processes create heat, the
worker is potentially exposed to heat-related illnesses because of the increase in
thermal load from the environment. For these workers to work a full 12 hour shift,
without developing any heat illnesses, their body temperatures must be kept within a
narrow range of 1 to 2°C (Joubert and Bates, 2008). Body temperatures
substantially higher than optimal temperatures (36.5-37.5°C) may cause a decrease
in the mental and physical performance of workers. Objectives: To evaluate the
heat strain experienced by furnace workers at an iron smelter. The evaluation will
include an anarysis of data for the full period of the shift (8 hours or 12 hours), as
well as the high risk periods (window periods). These window periods consist of the
tapping and cleaning time periods. Methods: Intra abdominal core temperature
was measured by means of a miniature data logging transponder for the duration of
the shift. This sensor transmits a wireless signal to a recorder worn on the worker's
waist. This method provides continuous measurement of core temperature with
limited work interference and no physical annoyance. Heart rate was measured with
Polar heart rate transmission straps and hydration by means of Urinary Specific
Gravity (USG). The Physiological Strain Index (PSI) was calculated using heart
rates and core temperatures. Environmental temperatures on the tap floor were
measured with a Heat stress instrument and 150 mm Globe for measuring radiant
heat. Results: Results indicated that cleaners and tappers of the 8h and 12h shift
experience moderate strain. Subjects were adequately hydrated and mean core
temperatures did not exceed the limit of 38.5°C for acclimatized individuals. Mean
WBGT○ values did not exceed the limit as given in ISO 7243, namely 26 for cleaners
and 28 for tappers. An analysis off each individual's data indicated inter-individual
differences. The group showing the highest amount of strain also had the highest
mean BMI. Conclusions: When evaluating heat strain it is important to evaluate
each individual's physiological indicators and not just general environmental
conditions. A subject's strain can be limited by applying adequate hydration,
acclimatization, work-rest ratios and engineering control measures.
Recommendations: Depending on the severity and intensity of heat strain there
are certain general- and job specific controls that should be applied to limit heat
strain. Always consider and include short term exposure in the investigation and not
just mean values for the day.
Collections
- Health Sciences [2060]