Epidemiology of organomercury poisoning in Iraq. III. Clinical features and their changes with time

Three categories of mercury poisoning were defined in the survey described by Al-Mufti et al. (see page 23) and the age-specific incidence rates for these are given. Persons with physical signs consistent with a diagnosis of organomercury poisoning were allocated to categories of severe disability or mild/moderate disability. However, the largest category consisted of persons who had symptoms but no readily elicitable physical signs at the time of the survey. These symptoms followed a consistent pattern with paraesthesia involving the lips and/or circumoral region or trunk and difficulty with walking, described as weakness or unsteadiness of the legs, and in some cases repeated falls, forming the most commonly occurring symptom complex. Mean maximum hair mercury levels differentiated this group very clearly from the group with no symptoms of mercury poisoning. Very few people in the area of low exposure complained of such symptoms; where they did occur they were less well related to the time of the outbreak and showed little tendency to improve. Most people reported improvement in their symptoms by the time of the survey, with more improvement in some symptoms than in others. However, it is not known whether those people with symptoms only at the time of the survey had had at an earlier stage mild signs which had cleared. It was thought unlikely that further substantial improvement would occur in those persons with disability at the time of the survey.