Exposure to airborne ceramic fibres the risk assessment

Exposure to airborne ceramic fibres: the risk assessment in a glassware factory Carelli G. , Iavicoli I. , De Rossi M. * and Cavariani F*. Occupational Health Institute – Catholic University of the Sacred Heart Largo F. Vito, 1 – 00168 Rome *Laboratory of Industrial Hygiene, Local Health Unit Viterbo – Via V. Ferretti, 169 – 01033 Civita Castellana (VT), Italy ICF Thirteenth Technical Exchange Conference – Siena, Italy 10 th – 12 th November, 2001

La classificazione cancerogeno non si applica alle fibre il cui diametro medio ponderato rispetto alla lunghezza meno due errori standard risulti maggiore di 6 mm.

Note R (EC Commission Directive 97/69, 5 th December 1997) Fibres whose mean weighed diameter compared to length (DLG) minus 2 standard errors (SE) are greater than 6 µm are not classified as cancerogenous DLG – 2 ES = exp[log DLG – 2 log LG n ] where: log DLG= i log (Di) Li/ i Li (log LG )2 = i (log Di - log DLG)2 Li/ i Li

aim of the study The field application of a sampling and analytical method to evaluate occupational exposure to airborne ceramic fibres among workers in a crystalware factory where ceramic fibres are widely used to insulate parts of high temperature furnaces

sampling and analytical methods Due to the lack of specific European and Italian regulations on the sampling and analysis of airborne ceramic fibres, we followed the criteria set out by the World Health Organization (WHO), Regional Office for Europe: Environmental Health. Reference methods for measuring airborne man-made mineral fibres. Copenhagen WHO/EURO/1985

sampling Environmental air was drawn through 25 mm diameter Nucleopore filters, pore size 0. 4 µm at the flowrate of 2. 5 l/min. This preliminary study included only area samplings (n=8) which were carried out also during the handling of the commercial product Kerlane. Sampling duration ranged from 1 to 4 hours (150 -600 l) The material safety data sheet of the product indicated the percentages (w/w) of Si. O 2 (45 -60%) and of Al 2 O 3(40 -55%)

samples • Eight samples were collected in three different areas of the factory during the warm-up of furnace and forehearths on day 1 and 2: • • • Area A: between forehearths (3 samples, day 1) Area B: between forehearths (3 samples, day 1) Area C: between furnace and forehearth (2 samples , day 2) results • Area A: < 1 fibre/l • Area B: < 1 -10 f/l • Area C: 2. 7 and 16. 3 f/l Note: the highest values have been obtained for samples C, during the maintenance of the refractory material

bulk (soft) sample

bulk (soft) sample microanalysis

bulk (dark) sample

bulk (dark) sample microanalysis

settled dust sample

settled dust sample microanalysis

airborne ceramic fibre collected by filtration

airborne ceramic fibre microanalysis

hygienic standard In order to evaluate the results in the absence of a European or Italian regulation, we referred to the indications of the Italian Ministry of Health Circular n. 4, dated March 15 th, 2000, which mentions the threshold limit value of 0. 2 fibers/cm 3 (200 fibres/l), proposed for refractory ceramic fibres by the American Conference of Governmental Industrial Hygienists (ACGIH) in the year 2001

Considerations • This study has shown that airborne refractory ceramic fibres can be found in crystalware factories where there is a wide use of such insulating materials • Analytical difficulties may arise if other types of fibres such as those of glass wool are simultaneously present in the airborne samples. In order to classify fibres correctly, microanalysis would be performed on all fibres sampled. This would entail heavy workload for laboratories if airborne fibres were numerous • Further analytical interferences in ceramic fibres count could arise from other airborne particulate. In fact dust contamination of workplaces can determine, in some instances, an overload of the sampling filter, thus impeding or preventing the examination of ceramic fibres

Considerations • In our opinion, the occupational threshold limit of 200 fibres/l adopted by ACGIH should be re-considered for “indirect exposures”. In fact, workers exposed to ceramic fibres in occupational sectors such as crystalware factories, are usually equipped with less protection devices than workers employed in ceramic fibre manufacturing or insulation activities, on account of presumably low levels to which they are exposed and the short duration of exposure. Furthermore we must remember the IARC classification of ceramic fibres as “probably cancerogenous to humans”. • Last but not least, recent studies have shown that at high temperatures (> 1200°C) ceramic fibres can be transformed into silica in the form of ’-crystoballite, -crystoballite and mullite (a crystalline silicate 3 Al 2 O 3. Si. O 2. Consequently exposure to silica could also occur in this type of environment.

Conclusions The preliminary findings of this study have shown that in the crystalware industry, ceramic fibers used for insulating parts of high temperature furnaces can become airborne To day this survey has been performed by area samplings during minor maintenance operations and will be completed with personal samplings before, during and after the removal of furnace insulation Analytical interferences such as those determined by an excessive presence of airborne dust or the problem of correct chemical identification of fibres collected could be eliminated by means of environmental and technological improvements

References • • Verein Deutscher Ingenieure: Measurement of inorganic fibrous particles in ambient air scanning electron microscopy method. Düsseldorf 1991 (VDI 3492 part I) World Health Organization (WHO) (1985), : Reference methods for measuring airborne man-made mineral fibres. Environmental Health, 4. Copenhagen WHO, Regional Office for Europe König AR, Hamilton RD et al. (1993) Fiber diametre measurement of bulk man-made vitreos fiber. Anal. Chim. Acta 280: 289 -298 Marconi A, Cavariani F. et al. (2001) Valutazione dell’esposizione a fibre ceramiche durante la coibentazione degli impianti di una centrale termoelettrica in costruzione. Med. Del Lavoro 92: 263 -271 Takahiro T, Yoshikazu K et al. (1999) Crystallization kinetics of mullite in alumina-silica glass fibers. J. Am. Ceram. Soc. 82: 2876 -2880 International Agency for Research on Cancer (1997): Silica, some silicates, coal dust and para aramid fibrils. Lyon: IARC (IARC Monographs on the evaluation of the Carcinogenic Risk of Chemicals to Humans, Vol 68) American Conference of Governmental Industrial Hygienists (ACGIH): Threshold Limit Values for Chemical Substances amd Physical Agents – Biological Exposure Indices (2001). Cincinnati: ACGIH, 2001 Commission Directive 97/69/EC of 5 December 1997 adapting to technical progress for the 23 rd time Directive 67/548/EEC on the approximation of the laws, regulations and administrative provisions relating to the classification, packing and labelling of dangerous substances. European Journal L 343, 13 th December 1997