Strategy For Limiting Risks Human Health Draft of ... - ECHA - Europa

2 The Risk Assessment
2.1 Workers
Introductory remarks
Occupational exposure to cryolite may occur during production and further processing and
use of the substance. This risk assessment is based upon the occupational exposure
assessment (RAR-chapter 4.1.1.2) and the toxicological profile of cryolite (RAR-chapter
4.1.2). The threshold levels identified in the hazard assessment are taken forward to
characterise the risks at the workplace and give indication for concern according to the MOS
approach as outlined in the TGD (Human Health Risk Characterisation, Final Draft).
Systemic availability for different routes of exposure
For cryolite information on absorption mainly comes from fluoride determination (F⎯) in
excrements (animal or human studies) after oral application. Very little is known on the
absorption and bioavailability of the aluminium-containing moiety. On the background of the
fluoride data the oral absorption in humans is assumed to be 95 % based on the study of
Largent and Heyroth (Largent and Heyroth, 1948). For animals, 85 % oral absorption is taken
for risk characterisation in animals (rats) based on the study of Wright and Thompson (1978).
Inhalation data are rare but give indication that also after inhalation of cryolite dust a
considerable amount of F⎯ may be absorbed. For inhalation a default value of 100 %
absorption is taken forward to worker risk assessment. For dermal absorption no data are
available. A value of 10% for dermal absorption of cryolite is assumed, because cryolite is
insoluble in organic solvents and thus will not easily pass the lipophilic stratum corneum of
the skin. Furthermore, salts are usually poorly absorbed via the dermal route. In all cases it
has to be recognised, that the information on absorption only applies to the F⎯ content of the
cryolite molecule.
Occupational exposure and internal body burden
In table 2.1 the exposure levels of the RAR-table 4.1 which concern cryolite are summarised
and the route-specific internal body burdens of F⎯ are identified. To this end the F⎯-content in
cryolite of 54% is taken into account in combination with the route-specific percentages for
absorption (100 % for inhalation and 10 % for dermal exposure). For combined exposure the
internal body burdens of F⎯ by inhalation and dermal contact are summed up to give a total
internal body burden.
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