Monitoring exposure to total volatile organic compounds and particulate matter at a petrol filling station

Abstract

Petrol-filling attendants in South Africa are occupationally exposed to hazardous chemical agents (HCAs), particularly volatile organic compounds (VOCs) associated with fuel handling and diesel particulate matter (DPM) generated from diesel-powered vehicle exhaust. In this context, it is important to distinguish clearly between these agents. Total volatile organic compounds (TVOCs) represent the aggregate concentration of multiple VOCs present in petrol vapours, whereas individual VOC constituents, such as benzene, toluene, ethylbenzene, and xylene (BTEX) are chemically distinct compounds with specific toxicological profiles. Similarly, diesel particulate matter (DPM) refers specifically to the submicron particles formed during diesel engine combustion, which differ in composition and health risk from general ambient particulate matter (PM). Exposure monitoring of three petrol attendants and one area was conducted during a 12-hour working shift over five consecutive days in a winter month (personal: n=15; area: n=5). BTEX and DPM were monitored by using conventional sampling methods in combination with real-time monitoring (RTM) of TVOCs and PM. Both personal and area monitoring of BTEX and DPM with results including elemental carbon (EC) and total carbon (TC) with the focus on EC were monitored by using NIOSH 1500/1501 and 5040, respectively and TVOCs and PM <0.8 µm (as an estimate of DPM) were monitored using RTM(ppbRAE 3000 and TSI SidepakTM AM520). No statistically significant difference was found between results for personal and area samples, nor between different days (personal monitoring), for BTEX and EC. However, a statistically significant very strong positive Spearman correlation (ρ = 0.975; p <0.05) was observed for personal benzene exposure and the amount of fuel dispensed. The exposure to TVOCs, while performing different activities, indicated a difference in exposure concentrations and peak concentrations up to 10 000 ppb while refuelling vehicles with petrol and lower peaks when refuelling vehicles with diesel. The lowest peaks were observed during vehicle assistant services and cash and retail operations. During the delivery of fuel and underground tank refuelling, petrol reached higher peaks, up to 7 000 ppb, than diesel, only up to 600 ppb. PM <0.8 µm (estimate of DPM)results of four different petrol attendants over a 12-hour shift indicated short-term peaks which were higher for smokers than non-smoking petrol attendants during the period of five minutes that they smoked. The comparison between the NIOSH 5040 and RTM methods for DPM indicated a strong agreement with minimal bias (personal: 0.050 49mg/m3 ± 0.058; area: EC 0.041 mg/m3 ± 0.043). Although exposure concentrations were below the regulatory limits of the adjusted 12-hour time-weighted average (TWA) occupational exposure limit (OEL), petrol attendants experience continuous low concentrations of exposure, which may pose long-term adverse health effects.