Heat strain in protective clothing following hot-wet or hot-dry heat acclimation

The purpose of the present study was to compare the heat strain while wearing nuclear, biological, and chemical (NBC) protective clothing following a hot-wet (HW) or hot-dry (HD) heat acclimation protocol. Twenty-two males were assigned to groups HW (n = 7), HD (n = 8), or control (C, n = 7). Subjects were evaluated during continuous treadmill walking while wearing lightweight combat clothing and during intermittent exercise while wearing the NBC protective clothing. While wearing Combat clothing, greater decreases in rectal temperature (Tre), mean skin temperature (Tsk), and heart rate were observed for both acclimation groups. For the NBC clothing trials, lower Tre, Tsk, and heart rates were observed only for group HW. The time required for Tre to increase 1.0 degrees C and 1.5 degrees C was significantly delayed for groups HW and HD. Sweat evaporation increased for HW, whereas no change was found for HD. The most significant changes in Tre, Tsk, and heart rate while wearing the NBC protective clothing occur following heat acclimation that involves wearing the clothing during exercise.

Oral and tympanic temperatures as heat strain indicators for workers wearing chemical protective clothing

Oral (Tor) and tympanic (Tty) temperatures were examined as alternatives for rectal temperature (Tre) as a heat strain indicator. Subjects were 20 male volunteers (age = 18-33 yr). A workload was determined in chemical protective clothing (CPC) by having the subject walk on a treadmill until a VO2 uptake of 1.33 (L/minute (approximately 650 W) was reached. At a second session subjects donned CPC and walked on the treadmill at the previously determined workload until Tre reached 39 degrees C, or heart rate reached 185 bpm, or volitional fatigue, i.e., one work cycle. Subjects then rested for 48 minutes. This cycle continued for 4 hours or until absolute fatigue at < 4 hours. Heart rate, Tor, Tty, Tre, and mean skin temperature were recorded every 10 minutes and at the end of work. A paired t-test was used to determine if a significant difference in the magnitude of temperature increase in Tor and Tty as compared with Tre existed. No significant difference (p > 0.05) was observed in delta Tor against delta Tre at 20, 30, 40, and 60 minutes of exercise, but delta Tor failed to display nonsignificant mean differences consistently throughout the test. However, delta Tty displayed no significant mean differences (p > 0.05) against delta Tre throughout the test. Tty significantly correlated with Tre at the 30- and 50-minute intervals (p < or = 0.05) and the end reading (p < or = 0.01). A repeated measures analysis of variance showed no significant difference between Tty and Tre over time. It was concluded that Tty has potential as a heat strain indicator for workers wearing CPC in the field, but Tor does not.

Efficacy of permethrin-impregnated uniforms in the prevention of malaria and leishmaniasis in Colombian soldiers

We determined the efficacy of the use of permethrin-impregnated uniforms for prevention of malaria and leishmaniasis in a double-blind, randomized study of Colombian soldiers on patrol. In the study of malaria, soldiers were issued impregnated uniforms (i.e., a shirt, an undershirt, pants, socks, and a hat) or uniforms washed in water; the soldiers wore the uniforms day and night for a mean of 4.2 weeks and were observed for an additional 4 weeks. Three (3%) of 86 soldiers wearing impregnated uniforms contracted malaria, whereas 12 (14%) of 86 soldiers wearing control uniforms contracted malaria (P = .015). In the study of leishmaniasis (soldiers were in the area of endemicity for 6.6 weeks and were observed for 12 weeks thereafter), 4 (3%) of 143 soldiers wearing impregnated uniforms and 18 (12%) of 143 soldiers wearing control uniforms acquired disease (P = .002). In the leishmaniasis study, and presumably in the malaria study, breakthrough infections in the treated group were primarily due to bites in unclothed regions of the body (face and hands). Permethrin-treated uniforms were virtually nontoxic (there were only two cases of mild skin irritation among 229 subjects), and impregnation is quick and inexpensive. Impregnation of clothing with permethrin is suggested for nonimmune populations who are likely to be exposed to malaria or leishmaniasis over a period of 1-2 months.

Heat loss caused by cooling the feet

The effect of cooling the feet to alleviate heat strain was examined. Subjects, wearing chemical protective clothing, immersed their feet in water at temperatures of 10, 15, 20, 25, and 30 degrees C after sitting for 120 min at 35 degrees C. Heat lost via the feet ranged from 151 +/- 15 to 55 +/- 5 W, being greater in the colder water. In a second experiment, subjects wearing chemical protective clothing and specially designed water-cooled socks walked on a treadmill at 5 km.h-1 and 2.5% grade for 90 min at 35 degrees C. Four conditions were examined: no cooling, cooling throughout the walk, cooling during the last 60 min, and cooling during the first 30 min. Rectal and skin temperatures and heart rates were monitored. Cooling for the first 30 min had little effect on the measured parameters, however, when core temperatures rose to over 37.5 degrees C, cooling during the last 60 min significantly attenuated the increase in body temperatures and heart rates. We conclude that this method could be used to alleviate heat strain.

Protective clothing and heat stress

The high level of protection required by protective clothing (PPC) severely impedes heat exchange by sweat evaporation. As a result work associated with wearing PPC, particularly in hot environments, implies considerable physiological strain and may render workers exhausted in a short time. Current methods of describing evaporative heat exchange with PPC are insufficient, will overestimate evaporative heat loss and should not be recommended. More reliable measures of the resistance to evaporative heat transfer by PPC should be developed and standardized. Direct measurements of evaporative resistance of PPC may be carried. However, a more promising method appears to be the definition of evaporative resistance on the basis of the icl-index for the fabric layers. The icl-index is a permeation efficiency ratio, which in combination with clothing insulation determines the evaporative heat transfer. Current methods should be further developed to account for effects of moisture condensation and microclimate ventilation.

Heat strain in the Canadian Forces chemical defence clothing: problems and solutions

The Canadian Forces chemical defence protective clothing can induce an overwhelming strain on one's ability to regulate body temperature. Recently a number of investigations have been completed at the Defence and Civil Institute of Environmental Medicine that focused initially on understanding the interaction of metabolic rate, ambient temperature, and ambient vapour pressure on the severity of heat strain associated with wearing the protective clothing. This paper presents a summary of these initial studies together with an overview of different attempts to reduce heat strain during exercise in a hot environment. Factors such as improved aerobic fitness or a period of dry heat acclimation have little if any benefit on tolerance time while wearing the clothing during light or moderate exercise. The best solution to the problem of heat strain remains the use of microclimate conditioning (personal cooling), and these techniques have been successful for Naval and Air Force personnel. For our Land Forces, however, microclimate conditioning is not feasible until a lightweight high-energy power source is developed.

The prevalence of atopy and hypersensitivity to latex in medical laboratory technologists

Members of the Alberta Society of Medical Laboratory Technologists were invited to take part in a study of sensitivity to latex gloves. A total of 230 persons volunteered; 108 (47%) had no problems with gloves, and 122 (53%) reacted to latex gloves. A history was obtained regarding atopy, smoking, years in laboratory medicine, and the nature of the problem with latex gloves. Serum was assayed for the total IgE level and the presence of IgE with specificity to common inhalant allergens and to latex. The affected group had an increased population of subjects with an atopic history and a higher incidence of a raised IgE level and a positive screen for inhalant allergens. In the affected group, there was no relationship between the total IgE level and severity of skin reaction. However, smoking was related to severity of reaction and was more common in the groups with a more severe reaction. Three subjects were positive for IgE specific for latex; there were no other data distinguishing them from latex-negative subjects.

[An anaphylactic shock reaction caused by latex from medical protective gloves]

In case of IgE-mediated latex allergy, the person wearing medical rubber gloves as well as the patient getting in contact with the gloves' outside may be affected. This is illustrated by the present case reports on two atopic young women. The first patient repeatedly underwent laparotomies and finally, 50 minutes after the onset of another operation, suffered an anaphylactic shock reaction due to transperitoneal latex resorption. The second patient was trained as an assistant in a dentist practice where she suffered more than once from latex contact urticaria as well as collapses. Since these were initiated by globus feeling, an aerogenic route of allergen penetration was assumed. Latex prick testing in this patient resulted in an anaphylactic shock reaction. With regard to these observations the general aspects of intraoperative allergen exposition and safety of latex skin testing are discussed. Recommendations are given for a) the latex test procedure in case of anamnestic suspicion of high-degree sensitisation, b) the issuing of a latex allergy pass, and c) the use of latex-free synthetic gloves.

Influence of temperature and metabolic rate on work performance with Canadian Forces NBC clothing

This study examined the effects of environmental temperature and metabolic rate on soldiers' work tolerance time (WTT) while wearing various levels of nuclear, biological, and chemical (NBC) defence protective clothing. There were 23 unacclimatized males (23 +/- 3 years, 76 +/- 8 kg, 1.77 +/- 0.08 m) assigned to exercise at either a light (walking 1.11 m.s-1 0% grade, alternating with lifting 10 kg) or heavy metabolic rate (walking 1.33 m.s-1 7.5% grade, alternating with lifting 20 kg) in an environmental chamber at either 18 degrees C, 50% R.H. (cool) or 30 degrees C, 50% R.H. (warm). Subjects were tested wearing three levels of clothing protection: combat clothing (L); combats and a semi-permeable NBC overgarment (M); combats and NBC overgarment, gloves, boots and respiratory (H). WTT was the time until rectal temperature (Tre) reached 39.3 degrees C, heart rate reached 95% maximum, dizziness or nausea precluded further exercise, or 5 h had elapsed. During the light and cool trials (N = 5), wearing M or H did not impair WTT (277 +/- 47 min). For the light and warm experiments (N = 6), WTT was significantly impaired with H (82.7 +/- 10.6 min). With the heavy and cool condition (N = 6), WTT was reduced with M (240.5 +/- 73.8 min) and H (56.7 +/- 17.9 min). Finally, during the heavy and warm trials (N = 6), WTT was progressively impaired for L (172.5 +/- 52.8 min), M (65.8 +/- 18.2 min), and H (34.0 +/- 9.7 min) levels of protection.(ABSTRACT TRUNCATED AT 250 WORDS)

Shoe concerns and foot problems of wearers of safety footwear

In Australia workers in many industries are required to wear safety footwear (footwear incorporating a steel toe cap). An investigation of the problems reported by 321 workers (70 per cent male) employed in a broad range of work activities and required to wear safety footwear was conducted in 1990 and 1991. Respondents were interviewed by a professionally trained podiatrist using a structured questionnaire followed by a foot examination. An extremely high percentage (91 per cent) of subjects reported one or more foot problems (which were verified by the podiatrist), and most considered that the safety footwear either caused the problem or adversely affected an existing foot condition. The main shoe concerns reported were excessive heat (65 per cent of all respondents), inflexible soles (52 per cent), weight (48 per cent) and pressure from steel toe cap (47 per cent). Certain gender differences were identified. General recommendations are made.

Decontaminating pesticide protective clothing

The review of recent work on the mechanisms of soil removal from textiles assists in understanding decontamination of pesticide protective clothing. The current work provides explanatory conclusions about residue retention as a basis of making recommendations for the most effective decontamination procedures. A caution about generalizations: Some pesticides produce very idiosyncratic responses to decontamination. An example is the paraquat/salt response. Other pesticides exhibit noticeable and unique responses to a highly alkaline medium (carbaryl), or to bleach (chlorpyrifos), or are quickly volatilized (methyl parathion). Responses such as these do not apply to other pesticides undergoing decontamination. Given this caution, there are soil, substrate, and solvent responses that do maximize residue removal. Residue removal is less complete as the concentration of pesticide increases. The concentration of pesticide in fabric builds with successive exposures, and the more concentrated the pesticide, the more difficult the removal. Use a prewash product and/or presoak. The surfactant and/or solvent in a prewash product is a booster in residue removal. Residues transfer from contaminated clothing to other clothing during the washing cycle. Use a full washer of water for a limited number of garments to increase residue removal. The hotter the washing temperature, the better. Generally, this means a water temperature of at least 49 degrees C, and preferably 60 degrees C. Select the detergent shown to be more effective for the formulation: heavy-duty liquid detergents for emulsifiable concentrate formulations and powdered phosphate detergents for wettable powder formulations. If the fabric has a soil-repellent finish, use 1.25 times the amount recommended on the detergent label. For water hardness above 300 ppm, an additional amount of powdered phosphate detergent is needed to obtain the same level of residue removal as obtained with the heavy-duty liquid detergent when laundering fabrics with the soil-repellent finish. The mechanical action of agitation increases dislodgement of particulate material. Too many items in the washing apparatus or too low water volume, or both, decrease agitation and soil removal. Bleach can be used if desired. Fabric softener does not affect pesticide absorption or residue removal in laundering. Dry cleaning is not recommended because the solvents used in dry cleaning may be recycled through dilution, filtration, activated charcoal adsorption, or distillation. Pesticides still may be present in recycled solvents and can be transferred from one item to another, or from one load to subsequent loads of dry cleaning.

The physiological consequences of simulated helicopter flight in NBC protective equipment

The physiological effects of wearing U.S. Army aviator nuclear-biological-chemical (NBC) individual protective equipment (IPE) were evaluated in the USAARL UH-60 research flight simulator. There were 16 male aviators who flew the simulator in 4 test conditions: standard flight suit and cool cockpit, standard flight suit and hot cockpit, NBC IPE and cool cockpit, NBC IPE and hot cockpit. The cool condition was a WBGT of 17.9 degrees C, the hot 30.6 degrees C. Rectal temperature, mean skin temperature, and heart rate were monitored and showed significant increases for the NBC hot condition compared with the other three. Seven subjects failed to complete the sortie in the NBC hot condition, with a mean survival time of 298 min. All subjects flew for the target 6 h in the other conditions.

'Top cover neuropathy'--transient brachial plexopathy due to body armour

Two cases of partial lesions of the brachial plexus (brachial plexopathy) occurring in soldiers wearing body armour are described. This is an occupational hazard which has not been reported before.

Plasma renin activity and aldosterone: correlations with moderate hypohydration

Adult male test subjects (n = 16) were assigned to one of three clothing configurations (Army fatigues, fatigues with impermeable chemical protective garments, and fatigues with protective garments plus protective masks) prior to exercise (level treadmill, 1.11 m/s, 50 min/h, 6 h) in a moderate (wet bulb globe temperature, WBGT = 23 degrees C) environment with ad lib water consumption. When protective masks were worn, two through-mask drinking systems were evaluated: the current gravity-fed system for fluid delivery and a new system utilizing a small hydraulic pump (Fist-Flex). Antecubital blood samples were taken prior to the start of and subsequent to the completion of exercise and analyzed for fluid-electrolyte regulatory hormones. During all trials with chemical protective garments, plasma renin activity (PRA) and aldosterone levels (PA) were significantly (p less than 0.05) elevated following the exercise protocol while neither was affected during exercise in fatigues only. Individual hypohydration levels during all trials ranged from low (0.84%) to moderate (4.04%). Levels of PRA were closely correlated (r = 0.635, t = 4.35, p less than 0.001) with hypohydration as measured by percentage of body weight lost during the 6 h trial. Likewise, PA was also correlated (r = 0.47, t = 2.81, p less than 0.01) with body weight loss. We concluded from this study that PRA and PA responses were exacerbated in moderate environments by the additional heat stress, sweat rate, and dehydration caused by the impermeable garments. Further, the logistical difficulty inherent in delivering fluid through the chemical protective mask reduced voluntary consumption, increased hypohydration, and elicited the greatest elevations in PRA and PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Stresses involved in wearing PVC supplied-air suits: a review

A side effect of the growth and development of industrial technology is the ever increasing number of hostile environments encountered by man. This situation has resulted in the development of impermeable clothing as a barrier protection against the external environment. Unfortunately, although specific government standards concerning the design and engineering requirements of the impermeable suit have been stated, little or no standardized evaluation of the majority of available suits has been attempted. This review was undertaken to provide an in-depth summary of the physiological effects of a PVC protective suit while working. It was concluded that it was necessary to develop a standardized performance test to determine the protective and stressful characteristics of the individual manufacturer's designed suit. Recommendations of specific criteria for the test were obtained.