this included only workers who had worked more than 50% of each day 's working period and had worked for at least 10 days of the follow - up period . information regarding the amount of liquid intake expressed ( in litres , l ) and daily productivity output ( in tons ) were recorded . the rehydration strategies were re - structured by decision makers participating in the project and the author of this paper . for an eight working hour schedule , all workers were instructed to drink 1 l of the rehydration solutions or tap water at least 30 minutes before they began to work . they were also encouraged to drink water and rehydration solutions ( 250 ml ) every 3045 minutes . in total , they were each asked to drink 10 l of liquid ( tap water and rehydration solutions ) per day . in order to facilitate the monitoring of basic heat stress indexes during the 2007/2008 harvesting season , temperature , humidity and dew point were measured by using a portable temperature monitoring device (  easylog , model el - usb-2 ) . variables such as heart rate and weight were evaluated at the beginning and at the end of the working day . neither the amount of liquid intake nor productivity was validated . wet bulb globe temperature ( wbgt ) values during the 2007 harvest season at montelimar farm descriptive statistics were used to analyse climate data ( temperature ( c ) ; relative humidity ( % ) ; dew point ( c ) ) ; liquid intake and output production . chi - squared test was used to evaluate liquid intake versus output production by using spss version 13 . descriptive statistics were used to analyse climate data ( temperature ( c ) ; relative humidity ( % ) ; dew point ( c ) ) ; liquid intake and output production . chi - squared test was used to evaluate liquid intake versus output production by using spss version 13 . 1 shows in situ hourly climate variation direct from the sugarcane fields while workers harvested the crop . as can be seen , temperature and relative humidity values oscillated from 23.5 to 34.5c and from 40% to 64% , respectively , reaching maximum values as early as 810 am . this meant that water distribution had to be started at around that time on an hourly basis . climate measurements during 160 working hours of follow - up for 22 sugarcane workers at the montelimar farm . table 2 shows the amount of liquid intake ( including both regular tap water and specially formulated rehydration drinks ) . what is of great concern is that , although temperature increased to maximum values early in the morning , many workers did not follow the rehydration measures and drank less than 6 l , a potentially dangerously low volume . comparison between temperature measurements and daily water intake for 22 sugarcane workers at the montelimar farm . this showed that 13 workers who had the highest production output ( range 68 tons , average 7.45 tons ) were those who drank more than 6 l of liquid ( regular tap water and/or specially formulated rehydration solutions ) in comparison to those who drank less liquid and had a smaller production output . relationship between production output and daily water intake for 22 sugarcane workers at the montelimar farm . measurements of heart rate and body weight at the start and end of the working day showed that workers experienced increases in heart rate and loss of body weight as they worked in these hot conditions . historically , monitoring of toxins in the work environment has been the primary focus for identifying risks . some potential biomarkers linked to cell injury are immunological factors , lymphokines , growth factors , prostaglandins , endothelins , collagen , adhesion molecules , thromboxanes , leukotrienes , platelet activating factors and heat shock proteins ( 10 ) . as mentioned earlier , heat illness is a major cause of preventable morbidity worldwide ( 1 ) and although human beings possess considerable ability to compensate for naturally occurring heat stress , many occupational environments and/or physical activities expose workers to heat loads which are so excessive as to threaten their health and productivity ( 11 ) . it is important to remember that the normal human body contains approximately 60% of water , the present project evaluated climatic conditions at sugarcane plantations located at sea level , on the southwest coast of nicaragua . monitored climate indices ( temperature and relative humidity ) values varied from 23.5 to 34.5c and from 40% to 64% , respectively , reaching maximum values as early as 8 am . according to the nicaraguan institute of territorial studies ( ineter ) ( 13 ) , relative humidity values for the whole month of april varied between 69 and 79% all along nicaragua 's pacific coastline from san juan del sur ( southern region ) to chinandega ( western region ) . managua lies between the two regions ; the montelimar sugar farm is located 62 km from managua . however , the ineter humidity data are quite different from the relative humidity registered on the farm located in western managua . temperature data were not available at ineter 's website . although only 22 subjects were followed - up for a short period of time in this study , important results were obtained . other authors have shown the relationship between heat stress health effects and the ability to perform different tasks , as well as the increased risk of suffering work - related injuries ( 14 ) . in this study , the workers drank more liquid as temperature values increased to maximum peaks . this was part of a rehydration process which was well planned in advance by the company 's decision makers . unlike during past harvesting seasons , when water and rehydration solutions were distributed quite randomly , during this harvesting season cool water and specially formulated drinks were distributed or intended to be distributed to workers , who received 1 l just before they began their working day and then 500 ml every 30 minutes . the basis of this principle is that drinking to satisfy thirst is not enough to keep a person well hydrated . most of the people become aware of thirst once they have lost 12 l of body water and persons highly motivated to perform hard work may incur losses of 34 l before serious thirst forces them to stop and drink . since dehydration reduces the capacity for absorption from the gut , workers must be educated regarding the importance of drinking enough water during work and continuing generous rehydration during off - duty hours ( 14 ) . there was a significant increase of production , with up to 8 tons per worker during the follow - up period compared to the normal 5.5 tons per worker prior to the change in rehydration measures . this important change in rehydration policies and increase in production output is the result of various efforts of training workers , foremen and managers on heat stress prevention , proper hydration measures and quality of ( working ) life carried out by occupational health and safety professionals ( physicians and engineers ) , human resources departments and top management at sugarcane farms . . often workers rejected the new rehydration measures , most of the time because it was difficult for them to understand thoroughly the dehydration and physiological compensatory mechanisms . some of the reasons for this can be attributed to their low educational level , and feeling that  nothing bad has ever happened to me before , etc . certainly more effort in terms of intervention strategies and scientific investigation needs to be carried out among workers in nicaragua who perform jobs in which they are exposed to high ambient temperatures . these include farm workers , construction workers , miners and fishermen , especially those employed in the informal sector , which occupies about half of nicaragua 's economically active population . more funds should also be designated by companies decision makers for improving basic working conditions , in order to increase overall productivity ( and workers satisfaction in terms of better wages ) . this would also translate into safer and healthier workers , less absenteeism from sick leave , fewer accidents and other incidents . the author has not received any funding or benefits from industry to conduct this study .
backgroundheat illness is a major cause of preventable morbidity worldwide . 
 workers exposed to intense heat can become unable to activate compensation mechanisms , putting their health at risk . 
 heat stress also has a direct impact on production by causing poor task performance and it increases the possibility of work - related morbidity and injuries . during the sugarcane harvest period , workers are exposed to excessive sunlight and heat from approximately 6 am to 3 pm . 
 a first assessment of heat stress during the 2006/2007 harvesting season served to redesign the existing rehydration measures . in this project , 
 sugarcane workers were provided with more rehydration solutions and water during their work schedule.objectiveto assess heat stress preventive measures in order to improve existing rehydration strategies as a means of increasing productivity.methodsa small group of 22 workers were followed up for 15 days during working hours , from 6 am to 3 pm . 
 selection criteria were defined : to have worked more than 50% of the day 's working schedule and to have worked for at least 10 days of the follow - up period . 
 a simple data recollection sheet was used . 
 information regarding the amount of liquid intake was registered . 
 production output data was also registered . 
 temperature measurements were recorded by using a portable temperature monitoring device (  easylog , model el - usb-2).resultsthe average temperature measurements were above the nicaraguan ministry of labour thresholds . 
 seven workers drank 78 l of liquid , improving their production . 
 output production increased significantly ( p=0.005 ) among those best hydrated , from 5.5 to 8 tons of cut sugarcane per worker per day.conclusionsproductivity improved with the new rehydration measures . 
 awareness among workers concerning heat stress prevention was increased .