Slags, elec. furnace smelting, iron silicate

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Acute/short term exposure

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

4 mg/m³

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

Additional information - workers

According to dustiness tests of Si/FeSi silicates, low or very low amounts of respirable dust and low amounts of inhalable dust can be detected. Based on this, inhalation DNELs are relevant for both the respirable and the inhalable fractions.

The DNEL for repeated dose toxicity of Si/FeSi silicate is based on lung effects which are considered as critical effects. There are currently no occupational limit values for this substance, but the German MAK commission (DFG 1991) has set a limit value of 4 mg/m³during an 8-hour shift for the inhalable fraction of amorphous silicon dioxide. For general dusts, the MAK commission set in 1997 a MAK value of 1.5 mg/m³for respirable dusts and 4 mg/m³for inhalable dusts to decrease the risk of general dust-induced chronic bronchitis (DFG 1997). These currently represent the lowest OELs for general dust in.

Repeated dose inhalation studies have been performed with different types of silicates (calcium silicate, kaolin and amorphous glass) at maximum concentrations of 10-27 mg/m³. No adverse effects were observed in any of these studies, and therefore no NOAEL or LOAEL which could be used for DNEL derivation has been identified.

Epidemiological data from different industries show that the occupational exposure to occupational dusts and fumes may increase the risk of chronic bronchitis/COPD. This also seems to be the critical effect in humans for ferrosilicon/silicon metal. In a recent study in the Norwegian ferroalloy industry (Johnsen et al., 2010), an annual additional decline in lung function, resembling the decline caused by smoking, was seen in Si/FeSi industry at a median exposure level of 2.3 mg/m³of general dust (representing thoracic fraction). According to the data from seven of these FeSi/Si plants, the median levels of respirable dust in this industry varied between 0.4 and 2.1 mg/m³(Elkem, 2005), the highest being at the furnace department. Median levels of respirable amorphous silica were ~0.1-1.3 mg/m3. No signs of fibrosis in workers were seen in these studies. However, since silicate particles are only a minor component of these dusts present in silicon/ferrosilicon factories, no conclusions on the inhalation toxicity and dose response of silicate can be made.

For practically insoluble particles like Si/FeSi silicate without general toxicity, the possible lung effects are most likely caused by general particle effects and not by toxicity caused by the substance itself. As no NOAEL has been identified, it is suggested that the recommendations by the German MAK commission (DFG 1997) for general inhalable dust (4 mg/m³) and respirable dust (1.5 mg/m³) should be used when setting DNELs. 4 mg/m³is also the value given for synthetic amorphous silica by the MAK commission (DFG 1991).

DNELs of 4 mg/m³(inhalable fraction) and 1.5 mg/m³(respirable fraction)are recommended for Si/FeSi silicate in occupational exposure.

General Population - Hazard via inhalation route

Systemic effects

Acute/short term exposure

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

2 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

Overall assessment factor (AF):

2

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

Additional information - General Population

According to dustiness tests of Si/FeSi silicates, low or very low amounts of respirable dust, and low amounts of inhalable dust can be detected. Based on this, inhalation DNELs are relevant for both the respirable and the inhalable fractions.

The DNEL for repeated dose toxicity of Si/FeSi silicate is based on lung effects which are considered as critical effects. There are currently no occupational limit values for this substance, but the German MAK commission (DFG 1991) has set a limit value of 4 mg/m³during an 8-hour shift for the inhalable fraction of amorphous silicon dioxide. For general dusts, the MAK commission set in 1997 a MAK value of 1.5 mg/m³for respirable dusts and 4 mg/m³for inhalable dusts to decrease the risk of general dust-induced chronic bronchitis (DFG 1997). These currently represent the lowest OELs for general dust in.

Repeated dose inhalation studies have been performed with different types of silicates (calcium silicate, kaolin and amorphous glass) at maximum concentrations of 10-27 mg/m³. No adverse effects were observed in any of these studies, and therefore no NOAEL or LOAEL which could be used for DNEL derivation has been identified.

Epidemiological data from different industries show that the occupational exposure to occupational dusts and fumes may increase the risk of chronic bronchitis/COPD. This also seems to be the critical effect in humans for ferrosilicon/silicon metal. In a recent study in Norwegian ferroalloy industry (Johnsen et al., 2010), an annual additional decline in lung function, resembling the decline caused by smoking, was seen in the Si/FeSi industry at a median exposure level of 2.3 mg/m³of general dust (representing thoracic fraction). According to the data from seven of these FeSi/Si plants, the median levels of respirable dust in this industry varied between 0.4 and 2.1 mg/m³(Elkem, 2005), the highest being at the furnace department. Median levels of respirable amorphous silica were ~0.1-1.3 mg/m³. No signs of fibrosis in workers were seen in these studies. However, since silicate particles are only a minor component of these dusts present in silicon/ferrosilicon factories, no conclusions on the inhalation toxicity and dose-response of silicate can be made.

For practically insoluble particles like Si/FeSi silicate without general toxicity, the possible lung effects are most likely caused by general particle effects and not by toxicity caused by the substance itself. As no NOAEL has been identified, it is suggested that the recommendations by the German MAK commission (DFG 1997) for general inhalable dust (4 mg/m³) and respirable dust (1.5 mg/m³) should be used when setting DNELs. 4 mg/m³is also the value given for synthetic amorphous silica by the MAK commission (DFG 1991). In order to consider the possibility that the general population may be more sensitive than the occupational population, an assessment factor of 2 was applied (inter-individual differences). Thus,the suggested DNEL for inhalable dust is 2 mg/m³and for respirable dust, 0.75 mg/m³.