. 2009 Apr;53(3):271–288. doi: 10.1093/annhyg/mep005

Table 2.

Summary of factors affecting metalworking aerosol fraction levels using multivariate statistical analysis

Aerosol fraction level, mg m⁻³	No. of measurements	Independent variables				Statistical model	Reference
Aerosol fraction level, mg m⁻³	No. of measurements	Machine (MT)/operation type	Engineering control type	MWF type	Other factors	Statistical model	Reference
Ln (total)	161	Grinding, vertical mill (-), aluminum machining (-)	Enclosed CNC, mechanical ventilation (-), LEV¥ (NS)	NS	Presence of welding at shop, shop height (-), peaked roof (-), ventilation (-), machine tools in which fluid is periodically changed (-)	Mixed effect model (R² = 0.77)	Ross et al. (2004)
Ln (thoracic)	161	Grinding, milling (-)	Enclosed CNC, LEV¥ (NS)	NS	Presence of welding at shop, no. of machines, shop height (-)	Mixed effect model (R² = 0.70)	Ross et al. (2004)
Ln (thoracic)	403	MT	NS	SS	Plant, FT1*MT	ANOVA (R² = 0.46)	Woskie et al. (1994a)
Ln (respirable)	403	MT	LEV (-) enclosure (NS)	SS	Plant type, indoor humidity(IH), outdoor temperature (OT), IHOT, MTFT2	ANCOVA (R² = 0.48)	Woskie et al. (1994b)
Ln (inhalable)	93	Grinding	Enclosure	NS	Plant type (NS), type of operation (single or multiple) (NS)	Mixed effect model (R² = 0.44–0.45)	Lillienberg et al. (2008)

Fluid type (FT1): straight, soluble, synthetic and semisynthetic; FT2: dry, straight (mineral), lapping (mineral), semisynthetic, soluble (emulsion) and synthetic; MT, machine type; CNC = computer numeric controlled; LEV¥ = local exhaust ventilation with no information provided as to the description of the system components such as enclosure, fan and cleaner; ANCOVA, analysis of covariance; NS = not statistically significant; SS = statistically significant. (-) indicates decreased level and ‘*’ indicates interaction effect.