Reducing dust exposure in indoor climbing gyms.

As users of indoor climbing gyms are exposed to high concentrations (PM(10) up to 4000 µg m(-3); PM(2.5) up to 500 µg m(-3)) of hydrated magnesium carbonate hydroxide (magnesia alba), reduction strategies have to be developed. In the present paper, the influence of the use of different kinds of magnesia alba on dust concentrations is investigated. Mass concentrations, number concentrations and size distributions of particles in indoor climbing gyms were determined with an optical particle counter, a synchronized, hybrid ambient real-time particulate monitor and an electrical aerosol spectrometer. PM(10) obtained with these three different techniques generally agreed within 25%. Seven different situations of magnesia alba usage were studied under controlled climbing activities. The use of a suspension of magnesia alba in ethanol (liquid chalk) leads to similar low mass concentrations as the prohibition of magnesia alba. Thus, liquid chalk appears to be a low-budget option to reduce dust concentrations. Magnesia alba pressed into blocks, used as powder or sieved to 2-4 mm diameter, does not lead to significant reduction of the dust concentrations. The same is true for chalk balls (powder enclosed in a sack of porous mesh material). The promotion of this kind of magnesia alba as a means of exposure reduction (as seen in many climbing gyms) is not supported by our results. Particle number concentrations are not influenced by the different kinds of magnesia alba used. The particle size distributions show that the use of magnesia alba predominantly leads to emission of particles with diameters above 1 µm.

Characterisation of individual aerosol particles on moss surfaces: implications for source apportionment.

The size, morphology and chemical composition of 8405 particles on moss surfaces (Hylocomium splendens) was investigated by scanning electron microscopy and energy-dispersive X-ray microanalysis. Two moss samples from three locations in Southern Norway (Algård, Birkeland, Neslandsvatn) and two sampling years (1977 and 2005) each were selected leading to a total of 12 samples investigated. At all three locations, particle deposition decreased substantially with time. The major particle groups encountered include silicates, iron-rich silicates, metal oxides/hydroxides, iron oxides/hydroxides, carbonates, carbon-rich particles, silicate fly ashes, iron-rich silicate fly ashes, and iron oxide fly ashes. Between 1977 and 2005, the relative number abundance of the three fly ash groups decreased substantially from approximately 30-60% to 10-18% for the small particles (equivalent projected area diameter <1 microm), and from 10-35% to 2-9% for large particles with diameters ≥1 microm. This decrease of fly ash particles with time was overlooked in previous papers on atmospheric input of pollutants into ecosystems in Southern Norway. In general, the presence of fly ash particles is ignored in most source apportionment studies based on bulk chemical analysis. Consequently, the geogenic component (crustal component) derived from principal component analysis is overestimated systematically, as it has a similar chemical composition as the fly ash particles. The high abundance of fly ashes demonstrates the need to complement source apportionment based on bulk chemistry by scanning electron microscopy in order to avoid misclassification of this important anthropogenic aerosol component.

Dust exposure in indoor climbing halls.

The use of hydrated magnesium carbonate hydroxide (magnesia alba) for drying the hands is a strong source for particulate matter in indoor climbing halls. Particle mass concentrations (PM10, PM2.5 and PM1) were measured with an optical particle counter in 9 indoor climbing halls and in 5 sports halls. Mean values for PM10 in indoor climbing halls are generally on the order of 200-500 microg m(-3). For periods of high activity, which last for several hours, PM10 values between 1000 and 4000 microg m(-3) were observed. PM(2.5) is on the order of 30-100 microg m(-3) and reaches values up to 500 microg m(-3), if many users are present. In sports halls, the mass concentrations are usually much lower (PM10 < 100 microg m(-3), PM2.5 < or = 20 microg m(-3)). However, for apparatus gymnastics (a sport in which magnesia alba is also used) similar dust concentrations as for indoor climbing were observed. The size distribution and the total particle number concentration (3.7 nm-10 microm electrical mobility diameter) were determined in one climbing hall by an electrical aerosol spectrometer. The highest number concentrations were between 8000 and 12 000 cm(-3), indicating that the use of magnesia alba is no strong source for ultrafine particles. Scanning electron microscopy and energy-dispersive X-ray microanalysis revealed that virtually all particles are hydrated magnesium carbonate hydroxide. In-situ experiments in an environmental scanning electron microscope showed that the particles do not dissolve at relative humidities up to 100%. Thus, it is concluded that solid particles of magnesia alba are airborne and have the potential to deposit in the human respiratory tract. The particle mass concentrations in indoor climbing halls are much higher than those reported for schools and reach, in many cases, levels which are observed for industrial occupations. The observed dust concentrations are below the current occupational exposure limits in Germany of 3 and 10 mg m(-3) for respirable and inhalable dust. However, the dust concentrations exceed the German guide lines for work places without use of hazardous substances. In addition, minimizing dust concentrations to technologically feasible values is required by the current German legislation. Therefore, substantial reduction of the dust concentration is required.