This work presents a monitoring study designed to evaluate workers' exposure to particles in several body shops within automotive plants. Concentrations in the proximity of welding activities were measured by a Fast Mobility Particle Sizer, several Condensation Particle Counters, a Nanoparticle Surface Area Monitor and a laser photometer, as well as by several gravimetric samplers. Average concentrations were found to be 1 x 10(5) part cm(-3), 3 x 10(3) mu m(2) cm(-3) and 0.4 mg m(-3) for number, surface area and PM, concentration, respectively (worst case). Very high concentrations, particularly for surface area, were observed in locations with a high density of manual resistance welding activities or close to oxyacetylene welding activities. Welding emission factors in the automotive plants were also evaluated and in the most critical body shop, the overall welding activities led to emission factors of 2.8 x 10(15) part min(-1), 7.0 x 10(6) mu m(2) min(-1) and 7.9 g min(-1) for number, surface area and PM(1) concentrations, respectively. Finally, particle concentration characterization, along with air exchange ratio measurements in the body shop, showed that the indoor concentrations and, hence, worker particle exposure can be reduced through the use of local exhaust ventilation. (C) 2011 Elsevier Ltd. All rights reserved.