What about dustiness?
Dust is an airborne solid particle. Dust particles are a major issue in working places, since exposure to high concentrations of dust can lead to occupational diseases that impair lung function. Irritation, asthma and cancer can all be caused by exposure to dust, even at low concentrations. This highlights the need to reduce the dusting potential of industrially produced compounds such as trace minerals.
Limits are set to minimize exposure to dangerous substances in the air, in order to protect workers at premix production sites. Occupational exposure limits (OEL) indicate the maximum exposure to dust in the workplace that is still considered as safe. For new authorisations, dust potential of feed additives is taken into account by the EFSA and the EU commission.
In general, selenium feed additives are considered to be dusty products. Selenium is known to be toxic upon inhalation (Dudley, H.C. 1938). People handling selenium products on a regular basis, such as workers in a premix factory, are at serious risk of being exposed to high levels of selenium dust which can impair health. In European Union, an OEL for selenium has been set at 0.2 mg Se/m3 of air. This value holds true for additives that have been registered after 2013. Previous, already existing EU authorisations have no limitations on dust potential.
The dust potential can be measured, by using the Stauber-Heubach dust meter. There is large variation in the dustiness of organic selenium sources. Orffa has analysed different selenium sources for their dustiness in collaboration with Delft Solids Solutions, an independent laboratory in the Netherlands (Table 2). For OH-selenomethionine, dustiness has been shown to be high, with values of 37.7 mg Se/m3 air. For the development of Excential Selenium 4000, Orffa has applied a special manufacturing procedure which ensures the product to be dust free and therefore complying with the OEL of 0.2 mg Se/m3 air. The low dusting level ensures the health of the workers that are handling the product, and also minimizes spilling, which allows optimal use of the product and therefore economic benefits.