The correlation between lung surfactant function inhibition in vitro and the effect on breathing of mice during inhalation exposure – A study of spray-formulated engine/brake cleaners and lubricating products

Moving parts in motors require maintenance, both lubrication for smooth operation and de-greasing for cleaning and repair. Since these motor parts are hard to reach, cleaning and lubrication products are often applied by spraying. However, the aerosol spray of the product can potentially reach the breathing zone of the worker and end up in the lungs. We investigated eight products and two single ingredients for their acute effects on the lungs. The effects of the aerosolized substances were tested in an in vitro model for lung surfactant function inhibition. The in vitro results were then compared to the effects of the aerosolized substances on the breathing parameters of exposed mice, measured in whole-body plethysmographs. No-observed-adverse–effect-concentrations were set based on the endpoint of reduction in tidal volume. When a reduction in tidal volume was used as the ´true´ result, the in vitro test for lung surfactant inhibition was 80% accurate at predicting if the substance affected tidal volume in exposed mice. The ranking of test substances were similar between the in vivo and in vitro results with the exception of (2-methoxymethylethoxy)propanol (substance A). This substance did not inhibit lung surfactant function, but was potent at reducing tidal volume in mice. In conclusion, lung surfactant function inhibition in vitro can be used as a screening tool for acute effects of ingredients in- or formulated -spray products on the lungs.