The variability of exposure over time: a prospective longitudinal study

Area of Science:

• Occupational Health and Safety
• Industrial Hygiene
• Environmental Monitoring

Background:

• Workers in factories face potential exposure to hazardous substances like lead, benzene, and dust.
• Assessing occupational exposure requires understanding the variability of contaminant levels over time and between individuals.

Purpose of the Study:

• To quantify the sources and magnitude of exposure variability in factory workers.
• To inform strategies for effective occupational exposure monitoring and compliance testing.

Main Methods:

• Conducted 440 personal air measurements on 54 workers across six factories over one year.
• Utilized a nested unbalanced analysis-of-variance model on log-transformed data to analyze exposure variance.
• Investigated the influence of factors like outdoor locations and worker mobility on exposure variability.

Main Results:

• Within-worker exposure variability accounted for 51% of the total variance (GSD = 3.1).
• Between-worker variance, primarily within factories, contributed significantly to overall exposure differences.
• Outdoor locations and worker mobility positively influenced both between-worker and within-worker exposure variance.

Conclusions:

• Accurate assessment of worker exposure necessitates considering both the mean and the within- and between-worker variance.
• Random, multiple measurements per year are essential to prevent worker misclassification.
• A geometrical standard deviation (GSD) of 3.1 can aid in calculating confidence limits for yearly exposure assessments.