Registration Dossier

Administrative data

Workers - Hazard via inhalation route

Systemic effects

Acute/short term exposure
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
DMEL (Derived Minimum Effect Level)
Value:
0.5 µg/m³
Most sensitive endpoint:
carcinogenicity
DNEL related information
Overall assessment factor (AF):
1
Acute/short term exposure
DNEL related information

Workers - Hazard via dermal route

Systemic effects

Acute/short term exposure
DNEL related information

Local effects

Long term exposure
Hazard assessment conclusion:
DNEL (Derived No Effect Level)
Value:
0.2 µg/cm²
Most sensitive endpoint:
sensitisation (skin)
DNEL related information
Overall assessment factor (AF):
5
Dose descriptor:
other: NOAEL

Workers - Hazard for the eyes

Additional information - workers

Inhalation DNEL / DMEL

Acute inhalation

In some exposure situations peak exposures may occur. Therefore a DNEL for acute toxicity might be needed. This can be derived using the LC50 value as a starting point. LC50 in the acute inhalation test with strontium chromate was 0.27 -0.51 mg/L . When taking the worst case situation as a starting point, the value used was 0.27 mg/L = 270 mg/m3.

For the extrapolation of the LC50 to a NOAEC an assessment factor of 100 was used.

For animal-human species variation the assessment factor was 10, and for worker inter-individual variability the assessment factor was 5.

This results in a total assessment factor of 5000.

The DNEL for acute inhalation would thus be 270 mg/m3 / 5000 = 0.054 mg/m3 = 54 µg strontium chromate/m3.

Long term inhalation / carcinogenicity

The genotoxicity of strontium chromate as well as the evidence of carcinogenicity from epidemiologic dose-response data (Park and Stayner 2006) do not allow derivation of threshold doses. Consequently, derived no-effect levels (DNEL) for carcinogenicity of Sr-chromate cannot be set, and instead, a DMEL has to be derived.

The data from high-quality epidemiologic studies enables the possibility to quantitative risk assessment of Cr(VI). A lot of risk assessment activities on occupational hexavalent chromium exposures were carried out when the background documentation for U.S. OSHA was compiled (see e.g. Park, Bena et al. 2004; OSHA 2006; Park and Stayner 2006). According to the assessments performed by OSHA, best estimates of lung cancer risks at an eight-hour averaged inhalation exposure level of 0.25 μg Cr(VI)/m3 are 0.52–2.3 per 1000 workers with a working lifetime of 45 years.

American Conference for Industrial Hygienists (ACGIH) has for strontium chromate suggested a TLVof 0.5μg Cr/m3

based on animal test data

. The 8-hour time-weighted occupational exposure limit in the USA (OSHA, based on epidemiological data) was adjusted to 5 μg/m3 for Cr(VI) in 2006. This is also the current limit value in Denmark and Sweden. In other European countries the limit is higher. The level of 5 μg/m3 is, however, clearly higher (10x10-3– 45x10-3) than advised in REACH guidelines. For the great uncertainties rising from the extrapolations to lower exposure concentrations, but taking into account precautionary reasons, a DMEL of 0.5 μg Cr(VI)/m3 is suggested for strontium chromate. The DMEL calculated for carcinogenicity is clearly lower than the acute inhalation DNEL. Based on this, the acute inhalation effects are considered to be covered by the very low inhalation DMEL derived for carcinogenicity. No DNEL is therefore proposed for acute inhalation.

Dermal DNEL

The DNEL for local dermal effects is based on skin sensitisation data. The DNEL calculations were performed according to appendix 8 -10 of ECHA guidance R8, and the article of Basketter et al. (2003), which is included under "skin sensitisation", and which is also one of the references listed in appendix 8 -10.

The starting point for the DNEL calculations was the results of a number of LLNA:s with potassium dichromate (Kimber et al. 2001). No such tests have been performed with strontium chromate and therefore this report with data on a more soluble chromate was selected. This is likely to result in a very precautionary estimate on DNEL.

The EC3 (Effect Concentration 3; concentration that induces a stimulation index of 3 or more) for potassium dichromate was 0.058%, which means that the substance belongs to the category of substances with extreme potency (appendix R.8 -10). The EC3 (%) can be converted to µg/cm2 (ECHA guidance R8):

0.058*250=14.5 µg/cm2 potassium dichromate, corresponding to 5.12 µg Cr/cm2

According to Basketter et al. (2003) this can be used as an NOEL. Chemicals with NOELs (derived from LLNA) ranging from 1 to 10 µg/cm2, have been grouped and a conservative NOEL of 1 µg/cm2 should be suggested for this group (Basketter et al. 2003).

For the derivation of DNELs the following assessment factors were used:

- Intraspecies variation: 1 (LLNA data correlates very well with human data, Basketter et al. 2003)

- Inter-individual varaibility: 5 (workers)

- Matrix effect: 1 (Dermal exposure to strontium chromate occurs for example via spraying paint. For this matrix an assessment factor might be needed. However, no AF was used in order to compensate for the the situation that strontium chromate is much less soluble (~1 g/L) than potassium chromate (~115 g/L) which was used in the LLNA. Due to the low solubility of strontium chromate, its skin penetration, and therefore its sensitisation potential, is likely to be much lower than that of soluble chromates like potassium dichromate.

- Use pattern: 1 (Basketter et al. 2003 used an AF of 3 for the use pattern whn calculating acceptable exposure levels for consumer products. However, in the case of strontium chromate, the exposure is unintentional and occurs only for very brief periods of time.

Based on the above mentioned NOEL and assessment factor (5), the DNEL for strontium chromate can be calculated as 1 µg/cm2 / 5 = 0.2 µg/cm2 as Cr(VI) (=0.78 µg/cm2 as strontium chromate).

As a comparison, it can be mentioned that the minimal eliciting threshold (MET)10% concentration for chromium allergic patients patch tested with potassium dichromate was 0.03 µg Cr(VI)/cm2/48 hours (Hansen et al. 2003), corresponding to 0.72 µg/cm2/2h of exposure (as Cr(VI)).

In appendix 8 -10 of ECHA guidance R8, it is stated that 'it is not appropriate to define elicitation thresholds as a function of skin sensitising potency' and the derivation of DNELs for skin sensitisers in the guidance is thus focused only on the induction phase. Accordingly, the DNEL suggested for dermal exposure to strontium chromate is based on the LLNA data.

General Population - Hazard via inhalation route

Systemic effects

Acute/short term exposure
DNEL related information

Local effects

Acute/short term exposure
DNEL related information

General Population - Hazard via dermal route

Systemic effects

Acute/short term exposure
DNEL related information

General Population - Hazard via oral route

Systemic effects

Acute/short term exposure
DNEL related information

General Population - Hazard for the eyes

Additional information - General Population