Paper on Heat Stress
Herbicide spraying is taking place with a hand-held spray. The sprayers carry a container of weedkiller on their backs and the spraying covers a large area which they are covering on foot.
The sprayers have just come back from annual leave, this being their first week back.
To protect themselves against the herbicide, they are wearing cotton coveralls and gloves.
On the day when spraying is to take place, the temperatures are measured at 11am.
They are: Globe temperature 43.50C Air temperature 32.00C Natural wet bulb temperature 20.00C * Calculate the WBGT * What work-rest program would you recommend? * What work-rest program would you recommend for workers who had been back for two weeks? * Suggest some other ways to prevent effects of heat stress in this case.
Answer 1: * WGBT= (0.7*NWB) + (0.2*GT) + (0.1*DB) = (0.7*20.0) + (0.2*43.5) + (0.1*32.0) = 25.9⁰C * Work-rest program: Since the workers have returned from a break around one month, they have to acclimatize themselves before taking full work load. The exposure time to heat must be shortened with frequent rest breaks. On an average an unacclimatized worker should rest for 15 min per hour. Such a work-rest cycle gives the worker’s body opportunity to lose excess heat. Thus preventing unwanted heat stress before acclimatisation. * Work-rest program for workers who have been back for 2 weeks: A time period of 2 weeks is sufficient for a worker to acclimatise himself to the work conditions. Since the WGBT is less than 27⁰C and the nature of work is moderate, the worker can carry on with his normal schedule. However, work should be planned in such a way that hectic part of the job can be done in the early morning when heat is not pressing. Heavy work should be avoided when the