Introduction Today traditional dust measurements are performed during one or at the most two working days and the results will represent the full year exposure. There is a large variation in exposure at a single company during the year depending on a lot of factors, such as production intensity, used Materials and methods, weather conditions, individual work pattern and behaviour. In this study traditional measurements were made during 2 time periods per company and the variance in measurements were studied.

Methods Personal sampling of respirable quartz was performed between April 2015 and February 2016 at one iron foundry and one bronze foundry. The measurements were made two days in a row, twice with two-three months in-between.

The air exposures of respirable quartz as personal measurements were performed for the full work day. A mixed-model was used to study differences between job titles and companies.

Results In total, 66 personal samples of respirable quartz were collected for 21 individuals. The quartz concentrations ranged between 0.0011–0.079 mg/m³.

The mixed-model analysis of respirable quartz show that the job titles and companies differs. Shakeout show a statistical significant increasing odds ratio of 2.4 (95% CI: 1.06 to 5.33) and the caster and melter has a significant decreasing odds ratio of 0.46 and 0.32 (95% CI: 0.24 to 0.89 and 0.19 to 0.53) compared to moulder as reference category. The quartz exposures at the iron foundry result in an odds ratio of 2.75 (95% CI: 1.70 to 4.45) compared to the bronze foundry. Between job titles represent 60.4% of the overall variance and the between worker within job title variance 25.5%.

Discussion The study implies that type of foundry and type of work at the foundry is a greater cause of the variance in the exposure then when in time the measurements are made.