dichloromethane; methylene chloride

Endpoint summary

Description of key information

Laboratory animal studies indicate that neat DCM is a skin and eye irritant. Respiratory tract irritation has been reported in humans exposed to high atmospheric concentrations.

Key value for chemical safety assessment

Skin irritation / corrosion

Link to relevant study records

Reference

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 404 (Acute Dermal Irritation / Corrosion)

GLP compliance:

not specified

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: ENKI-Konijnenfarm, Someren, The Netherlands
- Weight at study initiation: 2.5 - 3.0 kg
- Housing: individually, suspended, galvanized cages, fitted with a wire-mesh floor and front.
- Diet: ad libitum
- Water: ad libitum
- Acclimatization period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 +/- 3
- Humidity (%): >40
- Air changes (per hr): 10
- Photoperiod (hrs dark / hrs light): 12/12

Type of coverage:

occlusive

Preparation of test site:

shaved

Vehicle:

other: stabilized with amylene

Controls:

not required

Amount / concentration applied:

Amount(s) applied (volume or weight with unit): 0.5 ml

Duration of treatment / exposure:

4 hours

Observation period:

at 1, 24, 48, 72 hours, 9 and 16 days after the 4 hour exposure period

Number of animals:

Experiment 1 (dichloromethane tested individually): 3
Experiment 2 (dichloromethane examined simultaneously with three other solvents on separate skin areas): 3

Details on study design:

TEST SITE
- Area of exposure: 1 inch x 1 inch
- Type of wrap if used: patches fixed to the application sites by means of adhesive tape and the entire trunk of each rabbit was wrapped with an impervious material.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): with lukewarm water and soap
- Time after start of exposure: 4 hours

SCORING SYSTEM:
Method of Draize et al. (1944)

Irritation parameter:

erythema score

Basis:

animal: 4749

Time point:

24/48/72 h

Score:

4

Max. score:

4

Reversibility:

fully reversible within: 16 days

Irritation parameter:

edema score

Basis:

animal: 4749

Time point:

24/48/72 h

Score:

1.33

Max. score:

4

Reversibility:

fully reversible within: 16 days

Irritation parameter:

erythema score

Basis:

animal: 4750

Time point:

24/48/72 h

Score:

4

Max. score:

4

Reversibility:

not fully reversible within: 16 days

Remarks:

score 1 on day 16

Irritation parameter:

edema score

Basis:

animal: 4750

Time point:

24/48/72 h

Score:

1.67

Max. score:

4

Reversibility:

fully reversible within: 16 days

Irritation parameter:

erythema score

Basis:

animal: 4751

Time point:

24/48/72 h

Score:

4

Max. score:

4

Reversibility:

not fully reversible within: 16 days

Remarks:

score 1 on day 16

Irritation parameter:

edema score

Basis:

animal: 4751

Time point:

24/48/72 h

Score:

2

Max. score:

4

Reversibility:

not fully reversible within: 16 days

Remarks:

score 1 on day 16

Irritant / corrosive response data:

Experiment 1: Generally the following skin reactions were observed at one or more observation time points, up to 72 hours after treatment: well-defined or moderate erythema, very slight or slight oedema, slight focal haemorrhages (not after 72 hours), very slight ischemic necrosis (not after 4 hours), slight or moderate scaliness (after 48 and 72 hours), and slight incrustation (after 72 hours only). After 9 days, very slight erythema and very slight oedema (in all three rabbits), moderate or severe scaliness and very slight or slight incrustation (in two rabbits), and some superficial scars (in one rabbit); after 16 days, very slight erythema with or without very slight oedema (in two rabbits).

Experiment 2: Generally the following skin reactions were observed at one or more observation time points, up to 72 hours after treatment: well-defined or moderate erythema, very slight or slight oedema and very slight ischemic necrosis (not after 4 hours). After 9 days, well-defined erythema and very slight oedema (in two rabbits), slight or slight to moderate scaliness (in all three rabbits) and very slight incrustation (in one rabbit); after 16 days no dermal effects.

Interpretation of results:

Category 2 (irritant) based on GHS criteria

Conclusions:

According to the EEC-standards (as published in the Official Journal of the European Communities, L257, Volume 26, 16 September 1983) dichloromethane is irritating to skin but not corrosive

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Link to relevant study records

Reference

Endpoint:

eye irritation: in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Qualifier:

no guideline followed

Principles of method if other than guideline:

Investigation of DCM effect as a liquid or vapour on rabbit eye, by different methods: instillation of 0.1 ml or 0.01 ml liquid DCM in rabbit eye and 10 min exposure to 1750 or 17500 mg/m3 DCM vapour in 1 m3 exposure chamber.

GLP compliance:

no

Remarks:

did not exist at that time

Species:

rabbit

Strain:

New Zealand White

Vehicle:

unchanged (no vehicle)

Controls:

not required

Amount / concentration applied:

- 0.1 ml
- 0.01 ml (simulating splash contamination)
- 1750 mg/m3 (as a vapour)
- 17500 mg/m3 (as a vapour)

Duration of treatment / exposure:

The liquid DCM was instilled once.
The effects of DCM vapour were investigated as 10-min exposures

Observation period (in vivo):

at 10 min, 1, 6, and 24 h, and thereafter daily for 2 weeks

Number of animals or in vitro replicates:

92 animals total
18 for eye irritation studies,
12 for a histopathological evaluation of eye lesions,
24 for in vivo measurement of corneal thickness,
30 for measurement of intraocular tension, and
8 to assess the effect of therapy

Details on study design:

The liquid substance was instilled once into the conjunctival sac of the right eye, after which the lids were held together for a few seconds.
The effects of DCM vapour were investigated as 10-min exposures to 1750 mg/m3 or 17 500 mg/m3. Rabbits were exposed in a 1 m3 chamber using a "Spraying Systems" nozzle to generate the DCM aerosol, and the atmospheric concentration of DCM was continuously monitored by infra-red analysis

30 rabbits had 0.1 ml DCM instilled into the conjunctival sac of the right eye, of which;
6 animals were used for eye irritation studies,
6 for in vivo measurement of corneal thickness,
6 for measurement of intraocular tension, and
12 for a detailed histopathological study.

18 rabbits had 0.01 ml DCM instilled, of which;
6 were used for eye irritation studies,
6 for corneal thickness measurements, and
6 for intraocular tension measurements.

30 rabbits were exposed to 1750 mg/m3 or 17 500 mg/m3 vapour DCM.
From each group of 15 rabbits, 3 were examined for eye irritant effects, 6 used for measurement of corneal thickness, and 6 for measurement of intraocular tension.

Because of technical difficulties encountered in measuring intraocular tension after instilling 0.1 ml DCM, tensions were also measured in a further 6 rabbits receiving 0.02 ml DCM.

In the histopathological study of the effects of 0.1 ml DCM, rabbits were sacrificed by an intravenous overdose of sodium pentobarbitone at 6 h, and at 1, 2, 4, 7 and 14 days. Eyes and eyelids we're removed, fixed in 10% phosphate-buffered neutral formalin, and 6 μm-thick sections of paraffin blocked material stained with haematoxylin and eosin and by the periodic acid-Schiff technique.

8 rabbits were used to assess the effects of treating with a decongestant preparation after contaminating the eye with liquid DCM. The commercially available preparation Vasocon-A was used; this contains an antihistamine, antazoline phosphate (0.5% w/v), and an a-adrenergic sympathomimetic, naphazoline hydrochloride (0.05%). All rabbits had 0.01 ml DCM instilled; of these 4 had no further treatment, but the other 4 had a single drop of Vasocon-A instilled twice daily for 4 days, starting 15 min after contamination with DCM. Eyes were inspected for irritant effects and intraocular tension was measured at 1 and 6 h, and 1, 2, 3, 4 and 7 days.

Subjective assessment of irritant effects was made at 10 min, 1, 6 and 24 h, and thereafter daily for 2 weeks. Particular attention was paid to excess lachrymation, inflammatory changes in the eyelids (blepharitis), injection of conjunctivae, chemosis, sloughing, iritis, keratitis and vascularization of the cornea. Each effect was scored on a system whose guidelines were as follows:
Grade 0 - no effect
Grade 1 - a just detectable effect
Grade 2 - mild effect
Grade 3 - moderate effect
Grade 4 - marked effect
Grade 5 - severe effect with complication
Precise definition of the various grades for the different effects have been described by Ballantyne (1974, 1975). At the ends of the periods of inspection rabbits were sacrificed by an overdose of intravenously injected 6% sodium pentobarbitone, and their eyes removed for histological examination.

Corneal thickness was measured in vivo using an optical depth measuring device attached to a Zeiss slit-lamp microscope. Thickness was measured prior to contamination of the eyes, and then at 30 min, 1 and 6 h, and thereafter daily for up to 11 days. At every period of inspection 5 measurements were taken on each eye and the mean value recorded.

Intraocular tension was measured with a Draeger hand-held applanation tonometer. Control tensions were taken before contamination of the eye and, when chemosis was not so marked as to interfere with applanation measurements, at 10 min, 1, 5 and 24 h, and thereafter daily until tensions returned to normal.

Irritation parameter:

other: lachrymation

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 2.2

Max. score:

5

Reversibility:

fully reversible within: 8 days

Remarks on result:

other: volume of DCM: 0.1 ml

Irritation parameter:

other: blepharitis

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 1.9

Max. score:

5

Remarks on result:

other: volume of DCM: 0.1 ml

Irritation parameter:

other: conjunctival injection

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 2.1

Max. score:

5

Remarks on result:

other: volume of DCM: 0.1 ml

Irritation parameter:

chemosis score

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 2.8

Max. score:

5

Reversibility:

fully reversible within: 7 days

Remarks on result:

other: volume of DCM: 0.1 ml

Irritation parameter:

other: sloughing

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 1.1

Max. score:

5

Reversibility:

fully reversible within: 7 days

Remarks on result:

other: volume of DCM: 0.1 ml

Irritation parameter:

other: iritis

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 1.1

Max. score:

5

Reversibility:

fully reversible within: 8 days

Remarks on result:

other: volume of DCM: 0.1 ml

Irritation parameter:

other: keratitis

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 1.3

Max. score:

5

Remarks on result:

other: volume of DCM: 0.1 ml

Irritation parameter:

other: corneal vascularization

Basis:

mean

Time point:

other: 10 min, 1h, 6h, and daily up to 14 days

Score:

0 - 0.4

Max. score:

5

Remarks on result:

other: volume of DCM: 0.1 ml

Irritant / corrosive response data:

Flooding the rabbit eye with 0.1 ml liquid DCM caused moderate inflammation of the conjunctiva and eyelids, together with corneal injury. Excess lachrymation and chemosis persisted for about a week, and injection of the conjunctiva and lid margins for nearly 2 weeks. Iritis, occurring in two-thirds of animals, persisted for 1 to 7 days. Keratitis, varying from just detectable to marked, and accompanied by corneal neovascularization also occurred in those with iritis.
With 0.01 ml DCM, more equivalent to splash contamination of the eye, the inflammatory effects on conjunctiva and eyelid were just as marked as those occurring with 0.1 ml, but less persistent.

Other effects:

The potential of DCM to cause corneal injury was confirmed by the in vivo measurements of corneal thickness; a mean peak in-crease of 59% occurred at 6 h with thickness not returning to normal for 8 or 9 days. The histopathological findings of oedema, congestion, neutrophil infiltration, goblet cell proliferation and epithelial detachment of the conjunctiva, with neutrophil infiltration and denudation of the corneal epithelium are typical of chemical injury to the eye. However, both the macroscopic and histological observations demonstrated that healing occurs.
Although macroscopic signs of eye irritation were not apparent after ex¬posure to DCM vapour, small increases in corneal thickness occurred which were related to the degree of exposure.
Contamination of the eye with DCM, both liquid and vapour, caused increases in intraocular tension.

Interpretation of results:

Category 2 (irritating to eyes) based on GHS criteria

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Additional information

In animals, an available guideline study demonstrated that DCM can cause skin irritation in rabbits including severe erythema and oedema with necrosis. One investigation reported on the irritancy of DCM to the rabbit eye. Effects were reversible and included moderate to severe changes in the conjunctiva combined with increased corneal thickness and intra-ocular tension.

 

A few incidents (see 7.10.3) are reported in which DCM caused respiratory irritation in humans. Asphyxia was determined to be the cause of death in the case of a male worker who was subjected to accidental acute inhalation exposure (concentration unknown) for 1 hour; the autopsy revealed bilateral pulmonary congestion with focal hemorrhage. Respiratory symptoms (cough, breathlessness, chest tightness) were reported in incidents of acute inhalation exposure to DCM; no exposure levels were provided in this study.

A study of workplace exposure to 18–1200 mg/m3 DCM (geometric mean exposure of 127 mg/m3; 8 -hour TWA) in graffiti removers, showed irritation of the respiratory tract at concentrations above the at that time existing Swedish Permissible Exposure Limit (PEL) of 120 mg/m3 and Short-Term Exposure Limit (STEL) of 300 mg/m3. However, this irritation could also be as a result of other exposures as the workers were in underground stations in Sweden and exposed to a mixture of potential irritants. In fact, another study in humans found no effect on pulmonary function following repeated exposures to dichloromethane vapours (up to 1737 mg/m3). Thus, based on human data, dichloromethane might be irritating to the respiratory tract at high concentrations.

For irritating effects, no proper NOAEL or dose-response data are available and therefore no DNEL can be derived. Risk reduction measures are required to prevent the occurrence of skin and eye irritation and to guarantee safe use.

Justification for selection of skin irritation / corrosion endpoint:

Guideline study, GLP status not reported, available as unpublished report, fully adequate for assessment

Justification for selection of eye irritation endpoint:

Acceptable, well-documented publication, adequate for assessment

Effects on skin irritation/corrosion: irritating

Effects on eye irritation: irritating

Effect level: empty Endpoint conclusion: Adverse effect observed

Justification for classification or non-classification

Based on the available human and animal data, according to Directive 67/548/EEC criteria, the substance has to be classified as irritating to eyes (Xi; R36) and irritating to skin (Xi; R38).

According to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008, the substance should be classified Cat.2; H315 for skin irritation and Cat.2; H319 for eye irritation.

Based on human data dichloromethane might be irritating to the respiratory tract at high concentrations, as such no classification needed.