Comparing exposure zones by different exposure metrics using statistical parameters: contrast and precision

Area of Science:

• Occupational Health and Safety
• Environmental Science
• Aerosol Science

Background:

• Traditional mass concentration metrics for ultrafine particles are increasingly questioned.
• Alternative metrics like surface area (SA) and number concentration are proposed for nanoparticle exposure assessment.
• Effective exposure metrics are vital for accurate risk assessment and industrial hygiene practices.

Purpose of the Study:

• To evaluate the efficacy of different exposure metrics (SA, number, mass concentration) in differentiating workplace exposure zones.
• To compare the performance of these metrics in various industrial settings with nanoparticle aerosols.
• To determine the most suitable metric(s) for identifying nanoparticle exposure sources and zones.

Main Methods:

• Measurements of SA, number, and mass concentrations were conducted in designated high- and low-exposure zones.
• Study sites included a restaurant, an aluminum die-casting factory, and a diesel engine laboratory.
• Statistical parameters and concentration ratios were used to compare metric performance in distinguishing zones.

Main Results:

• In the restaurant and die-casting factory, SA and fine particle number concentrations significantly differentiated exposure zones, showing higher contrast and concentration ratios than mass concentration.
• Mass concentration failed to show significant differences in the restaurant and was less effective in the die-casting facility.
• No significant differences between zones were found for any metric in the diesel engine laboratory.

Conclusions:

• Surface area and fine particle number concentrations are superior metrics for differentiating nanoparticle exposure zones and identifying emission sources in many workplaces.
• Mass concentration is less effective for assessing ultrafine particle exposure in these settings.
• A multimetric sampling approach is recommended for comprehensive nanoparticle exposure assessment in occupational settings.