* Read in Section on Industrial Medicine and Surgery, Southern Medical Association, Forty-First Annual Meeting, Baltimore, Maryland, November 24-26, 1947.
In 1938, Foulger of the Haskell Laboratory of Industrial Toxicology, demonstrated that circulatory collapse induced by certain chemicals could be prevented both in laboratory animals and industrial workers through the addition of vitamin C in amounts up to 100 mg. to the diet. Since the symptoms and findings of heat exhaustion resemble those of circulatory collapse, it was reasoned that ascorbic acid might be used as a preventive against heat illness in industrial workers exposed to high temperatures and high humidity in whom heat exhaustion occurred in a known incidence.
During the summer of 1939, an opportunity arose to test this theory under controlled conditions.
In a large room, a group of workers (42 in number) engaged in the manufacture of a cellulose product, were routinely exposed to a temperature varying from 95 to 100° Fahrenheit with a relative humidity of 50. These men worked five days a week, eight hours a day. Heat exhaustion was known to occur in them. It became necessary to repair the ventilating system consisting of ducts and vents located near the ceiling of this room and the repair work had to go on during operation of this area. Maintenance workers from outside the area were brought in to do the repair work. It was decided to give the maintenance group 100 mg. of vitamin C daily and to use the regular operators as a control. Both groups were to receive seven grains of sodium chloride with three grains of dextrose hourly in the form of tablets. Both groups had physical examinations given them during the previous month and with the exception of minor defects, were essentially normal. The average age of the maintenance group was about nine years older than that of the operating or control group. The operating or control group had moderate physical labor to perform, whereas the maintenance workers had to perform hard physical work in awkward positions.
Due to the impairment of ventilation during this period, both temperature and humidity was elevated over a normal standard in the control group. The highest temperature to which they were exposed was 105° and the highest relative humidity was 84. Since the maintenance group was working next to the ceiling, they were exposed to temperatures from 100 to 120° Fahrenheit. During the same period, the outside temperature recorded a high of 92° with a relative humidity of 90. The lowest relative humidity registered on the outside was 62 as recorded by the Government Weather Bureau.
The maintenance group (31 men), were given 100 mg. of ascorbic acid in tablet form at 8:00 a.m. before going to work. At 11:30 a.m., blood pressures were taken in the sitting positions after a five-minute rest period. The highest systolic pressure was 138, the lowest recorded was 102. The highest diastolic was 94, the lowest 62. One individual’s diastolic pressure rose from 86 to 94, but this followed a weekend of drinking and was attributed to alcohol rather than heat.
During the 29 days that it took to finish this maintenance project, not one man receiving ascorbic acid in addition to sodium chloride, developed symptoms or findings of heat illness.
In the control group of 42 workers who received salt only, nine cases of heat exhaustion developed. These cases were not severe, incapacitating the employee for the rest of the day and thereafter necessitating several days of light work in a cooler area. Relatively few of these cases were accompanied by muscle cramps.
Following this period of controlled test for 29 days, all workers in this particular area were placed on 100 mg. of ascorbic acid. No cases of heat illness developed thereafter in these operators. In other areas where heat was a factor, namely: in the power house, the dryers, in the yard force exposed to summer heat and in certain locations of the chemical areas, heat exhaustion cases continued to occur in proportion to the rise in temperature, humidity, and physical labor performed, in spite of what we considered adequate salt intake.
Therefore we made available to all employees exposed to heat 100 mg. of ascorbic acid. As our employees became educated to the value of these tablets, our cases dropped in number. In 1938, previous to adopting this program, there were 27 cases which we recognized as heat exhaustion; in 1941, eight cases; in 1942, five cases, and in 1946 and 1947 no cases occurred. During these last two years, our educational program was intensified, and under direct supervision we gave these tablets to all employees who were exposed to degrees of heat sufficient to cause heat illness.
For reasons other than heat prostration, we added the B complex and A and D to the tablets in 1942. These multiple vitamin tablets were made available to more than 5,000 employees, about one-fourth of whom were exposed to heat which could under the right circumstances produce heat prostration.
In conclusion, thirty-one workers were exposed to temperatures and humidity conducive to the development of heat prostration for twenty-nine days. One hundred mg. of ascorbic acid was given daily to each of these workers. No case of heat illness developed in this group. Nine cases of heat prostration developed in forty-two workers in the same area exposed to a slightly lower temperature for the same period of time, who were given no ascorbic acid. No case of heat prostration has developed in any worker who has taken vitamin C, 100 mg. daily since this program was instituted in 1939.
Spruance Rayon Plant
Dr. Carl A. Nau, Galveston, Tex.—I should like to ask Dr. Weaver his explanation for his results.
Dr. Weaver.—I am unable to give any explanation for the observation that vitamin C in 100 milligram doses prevented heat prostration. A group of medical investigators in South Africa found a high incidence of scurvy in the native workers who were exposed to high temperatures in the mines. They concluded that this was due to the loss of vitamin C in perspiration. A group of American workers were reported to show little or no loss of vitamin C in the sweat. A Canadian worker recently has claimed that vitamin C plays a part in the maintenance of normal blood vessel tone through interaction with the hormones of the cortex of the suprarenal glands.
Dr. Nau.—In the one case to which you gave 300 milligrams, did you follow the blood pressure and capillary changes?
Dr. Weaver.—That case was not followed. He was a sub-contractor and therefore we had no physical examination on him when he was employed. He was brought to our medical department at 3:00 p.m. in collapse and was cyanotic. Respiration was around 40 per minute. The blood pressure was 144/120. The pulse was extremely rapid and thready. He was given 500 milligrams of vitamin C in solution in the vein very slowly. At 6:00 p.m. he was able to walk to a car and be transported home. He worked the next day at his regular work. Since the job was finished this day, he was not seen again.
In heat prostration you may find a rise in both systolic and diastolic pressure, or a drop in systolic and a rise in diastolic pressure, or you may have a drop in both systolic and diastolic pressure.
The usual case of heat prostration is treated by giving intravenously 1,000 c. c. of 5 per cent glucose in normal saline solution to which is added 500 milligrams of vitamin C and one of the preparations of B-complex which are put up for intravenous use. I was afraid to give intravenous fluid in this case, however.
Dr. Alexander Tish, Washington, D. C.—It would be interesting to hear if in these cases of heat prostration the vitamin C blood level was determined. If there were any such determinations, did you find a drop in the vitamin C blood level, rather than an increase in the excretion of vitamin C by way of the skin?
Dr. Weaver.—Some American investigators do not find any appreciable change or loss of C in the blood during heavy sweating.
Dr. Tish.—I do not understand the rationale for using vitamin C. More experiments should be conducted to explain the physiologic mechanism and to determine perhaps whether there is such a thing as susceptibility.
Dr. Weaver (closing).—In dealing with industrial workers, we are usually unable to obtain many blood samples. Workers object. The use of vitamin C to prevent heat prostration is purely clinical. It is effective with us in controlling heat prostration. It has been effective in other locations when used on my recommendation. During periods of high humidity and high temperature, we give our workmen these tablets and watch while they are taken.
From Southern Medical Journal, May 1948, Volume 51, Number 5, pp. 479-481
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