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

Long-Term Health Effects of Chemical Threat Agentsnerve agents in manufacturing plants, at depots, or inresearch and development facilities were relatively fewin number, tended to remain in the same job for a longperiod, and comprised closely knit groups. Most werethoroughly familiar with the effects of nerve agents,and most knew their coworkers very well. If a workerdid not seem “right,” his coworker or supervisor recognizedit. 122 A medical facility dedicated to the treatmentof nerve agent casualties, with a staff experienced inthis type of injury, was always available; workers wereencouraged to use it, and supervisors were instructedto send employees who were not “normal” to the medicalfacility for evaluation.One neuropsychiatric disorder that has been reportedto persist following the Tokyo incident is PTSD.Soon after the events in the Tokyo subway in 1995,one hospital reported that as many as 60% of patientsexhibited symptomatic PTSD up to 6 months after theinitial event. 124 Furthermore, 32% of the victims werestill feeling fear, 29% displayed insomnia, and 16% hadflashbacks of their experience. Still others displayeddepression (16%), irritability (16%), and persistent nightmares(10%). A 5-year follow-up of 34 patients involvedin the Tokyo incident 125,126 examined serum cholesterol,uric acid, cholinesterase, and PTSD. From this group,eight patients (23%) developed PTSD following theevent, and two were diagnosed with the disorder at thetime of the assessment. Comorbidity of PTSD with othermental illness, including anxiety, agoraphobia, panicdisorders, and severe depression, was also observedin the group that developed the disorder. Although norelationship of PTSD with cholesterol or uric acid wasapparent, the disorder had a surprising relationship toserum cholinesterase. Relative to patients who did notdevelop PTSD, the patients who developed PTSD hadlower serum cholinesterase both within 3 days of theattack and 5 years following the event. However, bothgroups had significantly reduced cholinesterase immediatelyfollowing the attack versus the 5-year assessment;thus, the relationship of reduced cholinesteraseand PTSD is not readily apparent.Other studies show the development of PTSD withrelated neuropsychiatric symptoms in sarin-exposedpatients following the Tokyo subway incident, butnot all showed persistent decreased cholinesterase. Agroup of 18 male and female sarin patients were neurobehaviorallyassessed 6 to 8 months following theterrorist incident. 127 Relative to matched controls, thesarin patients presented with significantly depressedcholinesterase activity at the time of hospital admissionthat had recovered by the time of the assessment.At the follow-up assessment the sarin patients showedsignificantly more psychiatric symptoms; fatigue; impairedWechslar Adult Intelligence Scale digit symbolperformance (a measure of motor persistence, sustainedattention, response speed, and visuomotor coordination);and extended latencies for P300 auditory eventrelatedand P100 visual brain-evoked potentials relatedto PTSD. The P300 evoked potential serves as a neuralmarker of the ability to allocate and sustain attention,and the P100 visual evoked potential is a marker for theconduction time from the retina to the visual cortex.In summary, studies intended to examine the neuropsychiatriceffects of organophosphate compoundsvary in their adequacy, and in some instances the resultsare contradictory. Most studies agree, however,that acute neuropsychiatric effects result from exposureto both insecticides and nerve agents. These effects includeinability to concentrate, memory problems, sleepdisturbances, anxiety, irritability, depression, problemswith information processing and psychomotor tasks,and potentially PTSD. With pesticides, these effectsdo not occur in the absence of the conventional signsof poisoning. The duration of these effects is less wellstudied. Some studies suggest that after exposure toinsecticides, problems might persist for a year or longer,but supporting data are not always provided. Thetwo reports of patients exposed to nerve agents andpersonal observation suggest that these effects are ofshorter duration in this class of compounds.Electroencephalographic AbnormalitiesInsecticides and Other OrganophosphatesElectroencephalographic abnormalities were reportedin subjects given daily doses of diisopropylfluorophosphate for 2 to 7 days. 128 These abnormalitiesconsisted of faster frequencies, higher voltages,and occasional bursts of slow waves of high voltageat 3 to 6 Hz. Their severity was directly related to thedegree of initial cholinesterase inhibition. The changespersisted for 3 to 4 weeks. Changes were noted in theelectroencephalograms (EEGs) of 50 industrial andagricultural workers within 72 hours of accidentalexposure to insecticides (both organophosphate andchlorinated hydrocarbons, on separate occasions),although the relationship to work history, blood cholinesterase,and exposure type, duration, and severitywere not mentioned. 113Nerve AgentsIn a patient severely intoxicated with sarin, an EEG(taken after the loss of consciousness but before theonset of convulsions) showed marked slowing, withbursts of high-voltage slow waves at 5 Hz in the temporofrontalleads. These abnormalities persisted for 6321