Oil shale, thermal processing waste

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.233 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

3

Dose descriptor:

LOAEC

AF for dose response relationship:

3

Justification:

Extrapolation from LOAEC to NAEC

AF for differences in duration of exposure:

1

AF for interspecies differences (allometric scaling):

1

AF for other interspecies differences:

1

AF for intraspecies differences:

1

AF for the quality of the whole database:

1

AF for remaining uncertainties:

1

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Most sensitive endpoint:

skin irritation/corrosion

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:

medium hazard (no threshold derived)

Additional information - workers

For the alveolar fraction (aerodynamic diameter <5 µm) of crystalline silica, epidemiological data indicate that the LOAEC (human) for silicosis is 0.05 mg/m³. Applying an assessment factor 3 to account for extrapolation from a LOAEC to a NAEC, results in a DNEL for the alveolar crystalline silica fraction of 0.017 mg/m³ [(0.05 mg/m³)/3]. No further assessment factors for workers are required as the LOAEC was determined from data of subjects occupationally exposed (8-10 h/day for a working lifetime) to respirable silica particles.

 

Comparable results are obtained from animal data. The lowest published toxic concentration for chronic inhalation exposure in rats is 0.74 mg/m³ (Muhle et al., 1991; NTP, 2009). Rats were exposed to crystalline silica particles (MMAD 1.4 µm) at that analytic concentration for 6 h/day, 5 days/week for 24 months.

 

A DNEL value for the alveolar fraction of crystalline silica is derived by applying the following corrections and assessment factors:

 

Step 1) Relevant dose descriptor	LOAECrat= 0.74 mg/m³
Step 2) Modification of starting point Correction differences between experimental and human exposure conditions Correction for differences in 8-h inhalative volumes between workers in rest and workers under light activity	(6 h/day)/(8 h/day)   6.7 m³/10 m³
Step 3) Assessment factors Interspecies Intraspecies Exposure duration Dose response Quality of data base	2.5 5 1 3 1
DNEL value for the alveolar crystalline silica fraction	0.01 mg/m³ (0.74 x [6/8] x [6.7/10] x [1/(2.5 x 5 x 3)])

 

Rather than the value based on rat data, the value of 0.017 mg/m³ obtained from human data is used as DNEL for the alveolar fraction of crystalline silica particles.

 

As the above mentioned DNEL values applies for the alveolar fraction of crystalline silica particles, DNEL values for burnt oil shale, total dust, are derived taking into account the content of respirable particles (≤4 µm) as well as the total quartz contents.

 

Chemical composition, granulometry and crystallinity data are available for 2 burnt oil shale samples:

 

 

Sample	P.1034	P.1082
Quartz content	22%	17%
Particles ≤4 µm (alveolar fraction)	33.4%	39.1%
Overall alveolar quartz fraction (assuming homogeneous distribution of quartz throughout all particle size fractions)	0.22×0.334= 0.073	0.17×0.391= 0.066
DNEL for alveolar crystalline silica (mg/m³)	0.017	0.017
DNEL for burnt oil shale, total dust (mg/m³)	0.233	0.258

 

The lower DNEL value of 0.233 mg/m³ is used for burnt oil shale, total dust.

General Population - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.233 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

DNEL derivation method:

ECHA REACH Guidance

Overall assessment factor (AF):

3

Dose descriptor starting point:

LOAEC

AF for dose response relationship:

3

Justification:

Extrapolation from LOAEC to NAEC

AF for interspecies differences (allometric scaling):

1

AF for other interspecies differences:

1

AF for intraspecies differences:

1

AF for the quality of the whole database:

1

AF for remaining uncertainties:

1

General Population - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Most sensitive endpoint:

skin irritation/corrosion

General Population - Hazard via oral route

Systemic effects

Long term exposure

Hazard assessment conclusion:

hazard unknown (no further information necessary)

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Most sensitive endpoint:

acute toxicity

Route of original study:

Oral

DNEL related information

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:

medium hazard (no threshold derived)

Additional information - General Population

The general public can be exposed to burnt oil shale in cement. The use of cement by the general population is infrequent and short-term/acute. Individuals using cement are healthy adults so that the intraspecies factor of 5 for workers can be adopted. Additional safety is introduced by using long-term epidemiological data as point of departure. Thus, the long-term inhalation DNEL for workers is adopted for the general population.