EVALUATION OF HEAT STRESS ON BAKERY WORKER IN MAKURDI BENUE STATE, NORTH EAST NIGERIA

publishing and ABSTRACT Nigeria being a tropical nation with high temperature and some Nigerian bakeries use mud oven which expose workers to direct contact with heat increasing their risk of heat stress. This research work tends to evaluate heat stress on bakery workers in Makurdi, Benue State. Forty questionnaires were validly filled and handed in from the workers at the various bakeries. Data such as age, duration of exposure as well as heat stress estimation and satisfaction level were filled in and data were analysis using statistics and results shows that heat stress reduces efficiency and productivity in workers poses health risk in workers such as heat cramps, heat rashes and in severe cases even heat stroke which may threaten the life of these workers. The results from measurements in this work has shown that bakery workers in Makurdi metropolis are highly exposed to heat stress and are likely to experience one disorder or the other with possible death consequences. It was also found that heat stress is often an overlooked problem as most workers lacked proper knowledge of control measures and employers have made little or no effort to prevent heat stress disorders.


INTRODUCTION
Heat is a form of energy characterized by an increase or a decrease in temperature, Heat may be defined as energy in transit from a high temperature object to a lower temperature object.
Stress can be defined as the brain's response to any demand. Heat stress occurs when the body's means of controlling its internal temperature starts to fail. Air temperature, work rate, humidity and work clothing are all factors which can cause heat stress. Climate in the work environment is an important factor in determining the physical comfort satisfaction of workers, and their comfort affects job satisfaction and performance. There are four primary variables that define climate, namely air temperature, humidity (relative humidity), air movement and radiation from surrounding objects including the sun. Environmental conditions cause body temperatures to rise above or fall below normal, there is a risk of either heat stress or cold stress. Nigeria being a tropical nation with high temperature and some Nigerian bakeries use mud oven which expose workers to direct contact with heat increasing their risk of heat stress. Heat stress reduces efficiency and productivity in workers poses health risk in workers such as heat cramps, heat rashes and in severe cases even heat stroke which may threaten the life of these workers. This research work is to establish the inherent heat stress amongst bakery workers and proffer solutions or suggestions to mitigate them. This work will help employers and owners of bakery to be more conscious of their workers' health and see ways to improve the conditions of their facility to reduce heat stress. It would also create awareness amongst workers to be mindful of their state of health as they work in high heat intensity facilities. It would also help engineers look at ways to create or remodel bakery facilities and equipment's in order to reduce the temperature around the working areas in bakeries thereby reducing heat stress.

LITERATURE REVIEW
The art of baking was brought into Nigeria by some freed Negroes who were well established as independent artisans in various trades. These Negroes educated and Christianized settled first in Lagos where baking was carried out in their homes until about 1900. Then, commercial bakeshops began to spring up. The eating of bread which was the main baked product at that time disseminated first along the coastline (Ports) Warri, Calabar, Port-Harcourt, and then inland Onitsha etc. The continued growth of the bakery industry necessitated the establishment of flour mill in Nigeria by the Nigerian government. A baker is a worker who mixes flour, salt, yeasts, spices, sugar, and other ingredients to prepare dough, batter, fillings, etc., which are then formed into bread, cakes, rolls, etc., and baked in an oven.  A recent study showed that workers in traditional bakeries are exposed to higher levels of heat stress when compared to workers in industrial bakeries. In addition, the incidence of heat stress among bakery workers in traditional bakeries has been shown to be 3.3% higher than those in industrial bakeries.

Heat stress checklist
An initial survey was carried out in each of the bakeries with the help of the heat stress checklist to ascertain their working condition. Each parameter is given a risk score and a brief description to help understand the score. The parameters that influences heat stress such as air temperature, radiant temperature, air velocity, humidity, clothing and metabolic rate were carefully observed as then given a risk score on the checklist according to how it is described by the checklist.

Questionnaires
The questionnaire was divided into 3 sections. Section A required that participants indicate their demographic information including their age, sex, job description. Section B assessed their work environment by asking participant to give information about how long they have been working in the bakery, how long they work and their shifts as well as their perception of the thermal environment and how much it affects them. Section C asked about experienced heat disorder and how often as well as if they have any form of education on heat stress and preventive measures.

Measurements of environmental parameters
Measurement was taken using a certified ADARSH wet bulb and dry bulb thermometer.
Measurement was taken during 10:00am and 2:00pm when most bakeries usually start the actual baking process. The hygrometer was first recalibrated, and then measurement was taken at three levels, above the head, at chest and below the waist level and the average was calculated.
Air temperature measurement was gotten reading the dry bulb thermometer and Relative humidity is determined by finding the differences in degrees between the dry-bulb and wetbulb readings on the horizontal scale at the top, and then reading off where this column intersects the horizontal row containing the dry-bulb temperature reading on a hygrometric chart.

Conversion tables
To determine the level of heat stress an operator is subjected to, an approximation conversion

RESULTS
This research was conducted in ten bakeries of which two used the traditional mud oven and eight used electrically powered oven in carrying out their work. Forty workers filled out questionnaires about their psychological description of their working conditions as well as other details. This is the results of the various methods used to conduct this research.

Heat stress checklist
The Mean Score of the Heat Stress Factors (Parameters) using Heat Risk Assessment Checklist is as shown in table 1 and 2.

Questionnaire and observation
Forty questionnaires were validly filled and handed in from the workers at the various bakeries. Data such as age, duration of exposure as well as heat stress estimation and satisfaction level were filled in. Table 3 shows that the participants are from all age group while Table 4 shows the duration which they have worked in the bakery. Table 5 gives us the psychological description given by the workers of the heat stress they are faced with and Table 6 tells us how much the heat stress affects their task in terms of their job satisfaction.

Measurements of environmental parameters
Two major hot rooms were identified at the bakery and these are (1) the furnace -which seemed to be an open space housing the oven and in some cases also the generator. This is where baking is actually carried out (2) the kneader -this is a closed room, this is where mixing, milling and pounding takes place before it is kept to rise and subsequently sent to be baked. Relative humidity and air temperature were measured as used to calculate the heat load the bakery workers are subjected to. The computed result is shown in tables 8 and 9.     At the furnace 130 Milling 100 Pounding 110 Mixing 120     reported cases of illnesses as well as symptoms of heat stress. Illnesses were ranging from minor fever to rare cases of yellow fever, while symptoms of heat stress such as fatigue, heat rash, headaches, heat cramps seemed to occur on daily basis or periodically as the case may be. Although no worker had a medically reportable case or severe symptoms of heat illness which caused them to cease work, their symptoms indicated that the physiological systems of the body were struggling to meet the demands of thermoregulation. Therefore, the primary avenue for reducing heat illness symptoms arising from this program of research is to improve the workers' hydration status and a point worth noting is that none of these bakeries had a well-organized system providing water for workers, most of the workers had to buy their own during break time which increases risk factor. Table 4 shows the assessment of the workers' heat rating during the baking task obtained from data collected through questionnaires. 97.5% of the respondents complained of feeling hot during the frying process, of which 40% rated the heat level as very high, and were exposed to this level of heat for a minimum of four hours. Table 5 shows that while most are uncomfortable with the heat level, it doesn't have much effect to their job attesting to the fact that they are acclimatized to the working conditions. Table 6 The values measured and calculated show that those at the kneader have a higher risk factor than those working at the oven. This is very unlikely hypothetically, since standing nearer to the oven sends direct heat to the worker but this was the case in bakeries visited due to 2 reasons. First, the oven is located in an open space with access to open air for ventilation while the kneader is a roomy space with very few windows for ventilation. This was said to be needed to help the bread rise faster. Secondly the kneader has an additional heat load coming from the milling machine as well as it was over populated. Table 7 Few workers worked at the oven compared to the millers, mixers as well as the pounders who work at the kneader resulting in higher temperature as well as higher humidity.
This gives an average of 38mins for those working in the oven and 29mins for those working at the kneader which implies that anything further than this could cause serious discomfort and increase risk factor. According to interviews as well as reports, all bakery workers work more than the tolerance time with some working more than six hours with a 1hr -2hr break. between heat stress index at the oven and ambient temperature in the oven is 0.789. Pearson's coefficient between the heat stress index at the kneader and its ambient temperature is 0.949. This is high relative to the Pearson's correlation coefficient between heat stress index at the oven and kneader and their respective relative humidity which is 0.585 and 0.421 at the oven and kneader respectively. This shows that air temperature has a higher significant value on heat stress as a rise in temperature would also increase heat stress. Relative humidity is not so significant call it depends on other factors such as water vapor pressure and air velocity. Table 9 No significant difference between heat stress at the oven and heat stress at the kneader was found (p>0.05). Also relationship between air temperature and relative humidity is not statistically significant (p>0.05) showing that one variable does not cause the other i.e. a rise in temperature does not necessarily mean a rise in relative humidity. The mean temperature of heat stress at oven and at kneader is significantly different from the required mean (p<0.05).
Also, statistically significant difference was seen between WBGT average of furnace in all bakeries (p<0.01). This issue is because of difference in bakery equipment's and varying weather conditions during which this research was carried out.
The result of the hypothesis test using ANOVA in Table 9 and 10 indicates that there is a significant difference between the indices for different workstations at F cal < F tab .
H o : the period (work station) the measurements were taken had no significant effect on the values collected (results obtained).