Bacterial-based additives for the production of artificial snow: What are the risks to human health?

Abstract

For around two decades, artificial snow has been used by numerous winter sports resorts to ensure good snow cover at low altitude areas or more generally, to lengthen the skiing season. Biological additives derived from certain bacteria are regularly used to make artificial snow. However, the use of these additives has raised doubts concerning the potential impact on human health and the environment. In this context, the French health authorities have requested the French Agency for Environmental and Occupational Health Safety (Afsset) to assess the health risks resulting from the use of such additives. The health risk assessment was based on a review of the scientific literature, supplemented by professional consultations and expertise. Biological or chemical hazards from additives derived from the ice nucleation active bacterium Pseudomonas syringae were characterised. Potential health hazards to humans were considered in terms of infectious, toxic and allergenic capacities with respect to human populations liable to be exposed and the means of possible exposure. Taking into account these data, a qualitative risk assessment was carried out, according to four exposure scenarios, involving the different populations exposed, and the conditions and routes of exposure. It was concluded that certain health risks can exist for specific categories of professional workers (mainly snowmakers during additive mixing and dilution tank cleaning steps, with risks estimated to be negligible to low if workers comply with safety precautions). P. syringae does not present any pathogenic capacity to humans and that the level of its endotoxins found in artificial snow do not represent a danger beyond that of exposure to P. syringae endotoxins naturally present in snow. However, the risk of possible allergy in some particularly sensitive individuals cannot be excluded. Another important conclusion of this study concerns use of poor microbiological water quality to make artificial snow.

Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments

“…5a therefore lie on the water saturation line. Only for Snomax ™ , an artificial snow inducer consisting of freeze-dried Pseudomonas syringae bacteria cells, cell debris and dried culture medium (Lagriffoul et al, 2010), deposition nucleation has been studied extensively (Chernoff and Bertram, 2010;Jones et al, 2011;Kanji et al, 2011;DeMott et al, 2011). More results on freezing experiments with biological particles, also from other habitats, are discussed in Després et al (2012).…”

Deposition nucleation viewed as homogeneous or immersion freezing in pores and cavities

“…Pores should therefore not be involved in ice nucleation on Snomax ™ particles. Considering the soluble material such as carbohydrates and nucleic acids that have been identified in Snomax ™ pellets (Lagriffoul et al, 2010), the ice active proteins should be immersed in an aqueous solution layer with bulk properties. In this case, ice nucleation on Snomax ™ would also occur by an immersion freezing mechanism in the reported cases of deposition freezing (Chernoff and Bertram, 2010;Jones et al, 2011;Kanji et al, 2011).…”

“…The product is obtained by the culturing of the bacterial cells, which are then centrifuged, frozen, lyophilisated, exposed to γ radiation and pressed into pellets consisting of bacteria cells, cell debris and a dried culture medium (Lagriffoul et al, 2010;Koop and Zobrist, 2009). The pellets are predominantly composed of proteins (30 to 50 %), carbohydrates (15 %), nucleic acids (10 to 11 %), metals (5 to 9 %) with alkaline earth salts (Ca, Fe, K, Mg, Na and P) and transition metals (Zn, Mn, Cu, and Ni) (Lagriffoul et al, 2010).…”

“…This protein is located on the outer membrane of the bacterium, with monomers of about 150 KDa (Lagriffoul et al, 2010). It contains a central repetitive region (around 1000 amino acids), which shows a close lattice match with ice and seems essential in the ice-producing activity (Kajava and Lindow, 1993).…”

Contribution of pollen to atmospheric ice nuclei concentrations

“…These particles can aid the nucleation of cloud droplets and ice crystals (Schnell and Vali, 1976;Möhler et al, 2007;Ariya et al, 2009) and thereby indirectly influence the Earth's climate system (Andreae and Rosenfeld, 2008). A small fraction of biological particles carry a protein that nucleates ice at temperatures slightly below 0 • C (Lagriffoul et al, 2010). Evidence of the presence of these proteins has been found in rain and snow samples (Christner et al, 2008a, b).…”