Evaluation of Ozone Exposure from use of Electrostatic Detection Apparatus

Use of Electrostatic Detection Apparatus in evaluating documents for hidden indentations creates ozone. Ozone can cause respiratory irritation and breathing difficulty. Ozone discharge was measured for an hour during continuous operation at two different locations. Results indicated that continuos use can generate ozone concentrations that will exceed the permissible exposure limit mandated by the Occupational Safety and Health Administration. Ozone levels can be controlled by shutting the corona off after creating static on the document and by using local exhaust ventilation. INTRODUCTION Electrostatic Detection Apparatus (ESDA) is used by forensic document examiners to visualize indented impressions in paper evidence, which may provide additional information in criminal cases. When using an ESDA, the document is first placed on the work surface and then covered with an imaging film (much like plastic wrap). The machine is turned on which seals the plastic wrap on the document. The corona wand is turned on and passed over the document surface. Toner beads are spread over the surface which fill in any indentations. The document can then be photographed. When the corona wand is used, the electric filament generates ozone gas. Ozone occurs naturally, being generated by ultraviolet light in the upper atmosphere and during lightning. Ozone is generated by electrical equipment and by automotive exhaust. Ozone generation during ESDA operation has been noted as potentially hazards to forensic document examiners (1). Human exposure to ozone can produce cough, soreness on deep inspiration, shortness of breath, chest tightness, dryness of mucous membranes. Non-respiratory effects include headache, nausea, weakness and dizziness (2). The US Environmental Protection Agency designates outdoor ozone levels of 0.12 ppm over an eight hour period in the National Ambient Air Quality Standards (3). The Occupational Safety and Health Administration (OSHA) sets an eight hour permissible exposure limit (PEL) for workers of 0.1 ppm. (4). The California OSHA also allows a 15 minute Short Term Exposure Limit (STEL) of 0.3 ppm (5). As part of a health hazard evaluation required by the California Department of Justice's Injury, Illness and Prevention Program, the two ESDA machines used by the Questioned Document Sections were measured for ozone generation in order to determine whether hazardous ozone levels were being produced. MATERIALS and METHODS The ESDA machine was activated according to the manufacturer's procedures. The Corona Wand was turned on and left on top of the ESDA. Ozone measurements were made with Colorimetric Indicator Tubes (Draeger #6733181, batch ARNH-5020) with an ozone detection level of 0.05 ppm (Figure 1). Ten pump strokes were required which took approximately three minutes per sample. Tubes were read immediately after the measurement was taken. Measurements were made without local ventilation and with local ventilation on.