Trifluoro(tetrahydrofuran)boron

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.95 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

Overall assessment factor (AF):

6

Modified dose descriptor starting point:

NOAEC

Acute/short term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

2.025 mg/m³

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

0.95 mg/m³

Most sensitive endpoint:

repeated dose toxicity

DNEL related information

Overall assessment factor (AF):

6

Dose descriptor:

NOAEC

Acute/short term exposure

Hazard assessment conclusion:

DNEL (Derived No Effect Level)

Value:

2.025 mg/m³

Most sensitive endpoint:

irritation (respiratory tract)

DNEL related information

Workers - Hazard via dermal route

Systemic effects

Acute/short term exposure

DNEL related information

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:

high hazard (no threshold derived)

Additional information - workers

Long term, inhalation DNEL (workers)

The toxicological effects of trifluoro (tetrahydrofuran) boron are basically driven by the toxicological properties of BF3 which is released from hydrolysis of this adduct in aqueous media. Hence, no further animal investigations are deemed necessary and for the DNEL it is proposed to overwrite the DNEL of BF3 or rather BF3 dihydrate on a molar ratio.

The subchronic study performed by Rusch et al. (1986) was considered as the study in which exposure was probably best reflecting occupational exposure conditions. In this study (Rusch et al., 1986), rats were exposed to aerosols of BF3 dihydrate for 13 weeks, the NOAEC was 6 mg/m3. Clinical signs of respiratory irritation were seen at all dose levels, but without abnormal histological findings. In addition, necrosis of the renal tubular epithelium was noticed.

For the derivation of the long-term DNEL, the starting point had to be modified according to Chapter R.8 of the REACH Guidance. Here, a correction for activity driven differences of respiratory volumes in workes compared to workers in rest was added to receive a starting point of 4.02 mg/m3. Additionally,an overall assessment factor of 6 was established: 2 for time extrapolation and 3 for intraspecies variability. The latter factor is lower than the dafault factor of 5 since the effects were considered to be mainly due to unspecific chemical reactivity of BF3 and hydrolysis to degradation products. No enzyme polymorphism is expected to be involved. No interspecies factor was used since the exposure route of the experimental study was inhalation. Thus, applying these assessment factors, a health-based occupational exposure limit of 0.7 mg/m3 was recommended for BF3 dihydrate. Based on the molar ratio of 1:1.3.5, an exposure limit of 0.95 mg/m3 was calculated for trifluoro(tetrahydrofuran) boron which is supposed to cover both local and systemic effects. This health-based exposure limit of 0.95 mg/m3 also covers the current German OEL of tetrahydrofuran which lies at 150 mg/m3.

Description	Value	Remark
Step 1) Relevant dose-descriptor	NOAEC: 6 mg/m3
Step 2) Modification of starting point	× 6.7 m3/10 m3	According to Chapter R.8 of REACH Guidance, correction for activity driven differences of respiratory volumes in workers compared to workers in rest.
Modified dose-descriptor	6 * 0,67 =4,02 mg/m3
Step 3) Assessment factors
Interspecies	1	No allometric scaling has to be applied in case of inhalation to inhalation route to route extrapolation.
Intraspecies	3	Default assessment factor for workers (decreased factor because no differences will be expected since no enzyme polimorphisms exist)
Exposure duration	2	Default assessment factor, extrapolation from sub-chronic to chronic
Dose response	1	Starting point=NOAEC
Quality of database	1
DNEL BF3 2*H2O	4,02 / (1 × 3 × 2 × 1 × 1) =0.7 mg/m3
DNEL C4H8BF3O	0.7 * 1.35 = 0.95 mg/m3 (Mol: BF3 2*H2O=103,  C4H8BF3O = 139.9 > ratio 1:1.35)

 

Short term inhalation DNEL (workers)

For the short-term DNEL of BF3 the German OEL of 1 mg/m3 has been employed with the following rationale: the ECHA guidance authorizes a registrant to use a national OEL in place of deriving a DNEL in case where toxicological information and evaluations of health effects used for setting the national OEL are documented and available. Therefore, it is proposed to use the German OEL (1 mg/m3 for BF3, equivalent to 1.5 mg/m3 for BF3 dihydrate) (http://www.baua.de/cae/servlet/contentblob/664358/publicationFile/47955/900-bortrifluorid-dihydrat.pdf) instead of the derivation of the DNEL. This OEL value is the lowest occupational exposure level in Europe, and is based on available and relevant toxicological data at present.

For the trifluoro(tetrahydrofuran) boron an equimolar DNEL of 2.025 mg/m³ is proposed.

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

Additional information - General Population

There are only industrial uses for BF3 and its THF adduct. The rejects of the substance in the environment (water, air) is extremely low. The general population is not exposed to these compounds via inhalation, dermal or oral route. Therefore, no DNEL is calculated for general population.