Arsenic

We evaluated the effects of arsenic and possible other chemical exposures from an arsenic trioxide-arsenic acid plant on residents of Bryan, Texas. We asked for volunteers from 156 plaintiffs in a class action suit certified to include 20,000-30,000 people who have been exposed to arsenic by living within the contour of 5 nanogram per cubic meter of air (ng/m3) defined by the United States District Court for the Southern district of Texas, Houston division. At this Atochem plant arsenic trioxide was used to produce a defoliant for cotton and converted to the arsenic acid pentavalent form for treating wood used in playground equipment. Other chemicals of potential concern packaged there included parathion, methylparathion, diazinon and manganese ethylene bisdithiocarbamate and zinc dimethyl dithiocarbamate.

The arsenic water-plume caused the Texas Water Commission to cite Atochem in 1992 for solid waste and water pollution by arsenic. Water contaminated with arsenic was used in the plant's cooling tower. The spread of arsenic in air was modeled and mapped by Dr. Colin Baynes with isopleths from 100 to 5 ng/m3 (Figure 1). Dust taken from 64 attics of homes in the vicinity of Atochem had median levels of arsenic of 16 (g/g and levels ranged from 1 to 813 (g/g. Within the 20 ng/m3 isopleth attic dust levels were >90 (g/g and even in the 10 ng/m3 isopleth levels were above 10 (g/g. A further water remediation plan was to react arsenic with ferric sulfate and sodium hydroxide and evaporate the residue. Organophosphates and carbamates were not found in attic dust samples.

The hypothesis was that arsenic impaired central nervous system function. These patients' symptoms suggested such impairment and a review of the literature did not show any reason to reject it. Thus, our objective was to determine whether a sample of the Bryan/College Station subjects named as class representatives in the lawsuit and non-participants from the same areas had neurological and psychological impairment. At the site, arsenic trioxide had been converted to arsenic acid to treat wood to make playground equipment for several decades.