Airborne organophosphates in the aviation industry : Sampling development and occupational exposure measurements

Abstract

During the last decade, there has been an increased concern of impact to human health from exposure to lubricants and organophosphates (OPs) for workers in the aviation industry. In spite of this concern, neither methods for assessing such exposure nor relevant exposure data for air concentrations of OPs could be found in the scientific literature. This revealed a need for development of such methods and work task related exposure measurements of OPs in the aviation industry in general. The four papers presented in this thesis describe development of sampling methodology and their use in the aviation industry for assessment of OPs in occupational air.<br> Paper I describes the method development needed for air sampling of OPs originating from lubricants such as hydraulic and turbine oils. Combinations of adsorbents, filters and extraction/desorption solvents were evaluated with respect to air sampling and analysis by gas chromatography–mass spectrometry (GC-MS) of six OPs* in presence of lubricants. The combination of Chromosorb 106 and 37 mm filter cassette with glass fiber filter and dichloromethane (DCM) as extraction/desorption solvent and tri-n-amyl phosphate (TnAP) as volumetric internal standard, was demonstrated to be well suited for sampling of airborne OPs originating from hydraulic and turbine oils.<br> While conventional pumped air sampling with a sampling train is documented in Paper I, Paper II describes development and evaluation of a semi-automatic sampler tailored for collecting volatile organic compounds, including certain OPs. This “incident sampler” is based on a pre-activated sampling unit that is stored at the work place of interest and a final simple activation performed by the worker that is subjected to the exposure. Intoxication of workers due to incidental chemical exposure has shown to be of high relevance. For instance, pilot incapacitation is the ultimate safety threat and consequently underlines the importance of revealing possible unknown contaminants in their working atmosphere. For that reason, the availability of an incident sampler in environments with risk of sudden chemical exposure is presented as an important tool to reveal possible contaminants from incidental air contamination. Ten such samplers were therefore installed in aircrafts within a 12 month period (Paper IV). However, neither of these aircrafts experienced such contamination incidents during this period, and the samplers were thus never activated during such incidents.<br> Paper III presents air measurements during loader and technician work operations. In total, 228 and 182 OPs and oil aerosol/vapor samples from technician and loader work tasks during work on 42 and 21 aircrafts, respectively, were collected in pairs. Additionally, 75 combined VOC/OP/oil and 40 combined OP/oil samples were collected from aircraft cargo rooms and from jet engine tail pipes during loading work operations, respectively, while 16 samples were collected during provoked situations related to technician work. VOCs and the butyl phosphates TnBP and DBPP were identified in most of the samples, most probably due to their frequent use and greater volatility than TCP. The highest TnBP exposure was during pressure drop in the wheel wells in one of the airplane models (maximum 9 mg/m3), and the butyl phosphates were also found to be present at background concentrations of 1-30 μg/m3. The potential for higher exposure levels during worst case situations was also investigated, for instance by exposure provocations and direct measurements close to the exposure sources such as jet engine tail pipes where maximum oil aerosol and TCP levels were 240 and 30 mg/m3, respectively.<br> Measurements of contaminants in cabin air are presented in Paper IV. A set of tailored sampling methods were applied, including development of new long-term sample methods based on deposition to a wipe surface area and an activated charcoal cloth installed on walls inside the airplane. In total, 167 pumped within-day OP/VOC samples and 108 longterm samples were collected in cabin and cockpit air from 40 unique aircrafts during 47 commercial flights. Total-VOC was measured using sampling with thermal desorption tubes, and was determined in all 71 such samples (min-max 0.20-2.7 mg/m3). For pumped within-day air sampling, TnBP levels were highest in model A airplanes and were detected in all airplane flights (n=76, min-max 0.02-4.1 μg/m3), while TCP was detected only on samples collected from four flights in model C airplanes (min-max <LOQ-0.29 μg/m3). TCP was, however, present in 11 out of 12 long-term wipe samples in model C airplanes and in all six HEPA filters from model A airplanes (1.1-42 ng/g per flight hour). TCP concentrations during ground testing in an airplane that had experienced leakage of turbine oil with subsequent contamination of the cabin and cockpit air, was an order of magnitude higher (5.1±1.1 μg/m3) as compared to after engine replacement (p=0.02) during ground test.<br> The four papers presented in this thesis thus encompass new air sampling methodologies and their application for characterization of OP contamination levels in the aviation industry, in addition to determination of oil aerosol and tVOC. This has resulted in collection of nearly 900 samples during general work tasks for technician and loaders, and in cockpit and cabin air during commercial flights, which is a substantial contribution to the knowledge of occupational exposure to OPs in this industry.