Medical Aspects of Chemical Warfare (2008) - The Black Vault

Occupational Health and the Chemical Surety MissionWorkplace, 13 these employees are also subject to randomdrug testing.The physician who reviews positive urine drug testsfor the Army is currently a certified medical reviewofficer. If the IMA fills this position, it is important forthe physician to review drug tests independently ofhis or her surety duties. The IMA is legally bound toperform an impartial review of the medical evidencefor a federally mandated positive test and then releasethe results only through proper channels. This taskmay be difficult, given the responsibility of suretyduties; the physician must always use sound medicaljudgment backed by legal advice.Heat Stress Physiologic MonitoringHeat stress is a constant and potentially severehealth threat to employees wearing toxicological protectiveclothing. The combination of exposure to solarradiant energy or enclosed areas with high temperatures,metabolic heat production, and the use of impermeableclothing (which prevents evaporative cooling)places the chemical worker at high risk for heat injury.Encapsulating uniforms increase the heat strain associatedwith most environments and work rates bycreating a microenvironment around the worker. Thesuit’s impermeability to vapor (the characteristic thatmakes it protective) creates high local humidity, restrictingevaporative cooling and conductive/convectivecooling. In effect, the suit creates an environmentat the body surface hotter and wetter, under almostany circumstances, than the environment outside thesuit. Moderating the heat strain associated with anencapsulating ensemble is accomplished in the followingways:• microclimate cooling by direct removal ofheat, water vapor, or both from the worker’smicroenvironment;• heat sinks in the suit, such as ice vests;• increasing the temperature gradient acrossthe suit by shielding workers from radiantheat sources, cooling the work space, or, indry environments, wetting the surface of thesuit; and• work–rest cycles to permit cooling and rehydration.Heat-induced occupational injury or illness occurswhen the total heat load from the environment andmetabolism exceeds the cooling ability of the body.The resulting inability to maintain normal body temperatureresults in heat strain (the body’s response tototal heat stress). 14Adverse health effects can be reduced by trainingand acclimatization, measuring and assessing heatstress, medical supervision, heat-protective clothingand equipment, and properly applying engineeringand work-practice controls. 14 Training and adequatesupervision are basic requirements that need constantreinforcement. The occurrence of heat-induced illnessor injury is an indication that (a) the worker hasengaged in an act that should have been avoided byadequate training and supervision, (b) the individual’smedical status has changed and requires further ormore frequent evaluations, or (c) supervisory enforcementof work–rest cycles or adequate hydrationis lacking. In all cases, the healthcare provider mustinvestigate the cause. If the individual’s health statushas changed, further medical evaluation is needed. Theworker may require temporary duties commensuratewith his or her present health status or a permanentchange of duties. If the injury appears to be the resultof carelessness or lack of attention to changing environmentalconditions, further training is needed. Elicitingthe worker’s support may be necessary to acquire theappropriate cooperation of intermediate supervisors.Numerous textbooks and other sources discussthermoregulation and physiological responses to heat,and healthcare providers may benefit from a review ofthese subjects. This chapter, however, will address theevaluation of heat stress and preventive measures.The preplacement physical examination is designedfor workers who have not been employed in areasexposed to heat extremes. It should be assumed thatsuch individuals are not acclimatized to work in hotclimates. Therefore, the physician should obtain thefollowing information 14 :• A medical history that addresses the cardiovascular,respiratory, neurological, renal,hematological, gastrointestinal, and reproductivesystems and includes information onspecific dermatological, endocrine, connectivetissue, and metabolic conditions that mightaffect heat acclimatization or the ability toeliminate heat.• A complete occupational history, includingyears of work in each job, the physical andchemical hazards encountered, the physicaldemands of these jobs, the intensity and durationof heat exposure, and any nonoccupationalexposures to heat and strenuous activities.The history should identify episodes of heatrelateddisorders and evidence of successfuladaptation to work in heat environments aspart of previous jobs or in nonoccupationalactivities.603