Slack wax (petroleum)

Endpoint summary

Description of key information

One key read-across study (API, 1986a) was used to evaluate the dermal irritation potential of slack wax (carcinogenic or unknown feed-stock). The primary irritation index was 4.3 thereby classifying the test material (an unrefined light paraffinic oil) as moderately irritating. Two key read-across studies (Exxon Biomedical Sciences, Inc, 1988a and NOTOX, 2003a) were used to evaluate the dermal irritation potential of slack wax (non-carcinogenic feed-stock). In a human volunteer study, the test material (an other lubricant base oil, IP 346 <3 wt%) did not produce more than a faint to moderate response in the skin of the 112 participants. In a study in rabbits, slight erythema, fully reversible by 24 hours, was observed 1 hour post administration. Paraffin wax was considered to be not irritating in this study.

One key read-across eye irritation study (API, 1986a) was identified for slack wax (carcinogenic or unknown feed-stock). The test material (an unrefined light paraffinic oil) did not cause a pain response, corneal or iridial irritation and any eye irritation that occurred had cleared by 48 hours.

Two key read-across studies (API, 1982e and CTFA, 1980) were identified for slack wax (non-carcinogenic feed-stock).  In one study, at the 72-hour observation period, application of the test material (another lubricant base oil, IP 346 <3 wt%) did not result in any irritation in rabbits with washed eyes. A single male rabbit in the unwashed group exhibited conjunctival chemosis at the 48-hour observation period. In another study, 0.1 millilitres of a 50% paraffin wax in petrolatum solution instilled into the eyes of six albino rabbits without rinse was also observed to be not irritating.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Slack waxes are waxes with entrained oils. Since paraffin and hydrocarbon waxes are non-hazardous the category hazard profile is determined by the entrained oils. Since the entrained oils are a minor portion of the slack waxes, this is considered to be a worst-case approach.

Slack Waxes (Carcinogenic or Unknown Feed-stock)

Read across justification

No dermal or ocular irritation studies have been reported for slack waxes (carcinogenic or unknown feed-stock), but data have been reported for unrefined / acid treated lubricant base oils and paraffin waxes, materials similar to the oil entrained in slack waxes (carcinogenic or unknown feed-stock).

Skin Irritation:

One key read-across study (API, 1986a) was identified for evaluating the skin irritation potential of slack wax (carcinogenic or unknown feed-stock).

In this study, 0.5 mL of undiluted test material (API 84-01, an unrefined light paraffinic oil, (CAS No. 64741-50-0)) was applied to the shorn dorsal skin in two areas on 6 male white rabbits. One area was intact and the other area had abraded skin. The treated area was covered with an occlusive dressing and 24 hours subsequent to test material application, the dressing was removed and treated skin wiped to remove any residue. The degrees of erythema and edema were recorded according to the Draize scale. A second reading of skin responses was made at 72 hours and again at 96 hours, 7 and 14 days. Results of the 24 and 72-hour readings were used to determine the Primary Irritation Index which was 4.3. Thus, the test material was judged to be moderately irritating. It should be noted however, that the procedure used, i.e., 24 hour exposure period with an occlusive dressing was more severe than the 4-hour exposure period with semi-occlusive dressing which is the basis for dermal irritation classification in the EU.

Eye Irritation:

One key read-across eye irritation study (API, 1986a) was identified to evaluate the eye irritation potential of slack wax (carcinogenic or unknown feed-stock).

In a key study (API, 1986a), 0.1 mL of undiluted test material (API 84-01, an unrefined light paraffinic oil (CAS No. 64741-50-0)) was applied to the corneal surface of one eye of each of 9 rabbits; the contra-lateral eyes were untreated and served as controls. After 20-30 seconds, the treated eyes of 3 rabbits were washed with lukewarm water for 1 minute. Eyes of the other 6 rabbits were not washed. Observations for ocular lesions for all animals were made at 1, 24, 48, 72 hours and 7 days after treatment. Sodium fluorescein was used to aid in revealing possible corneal injury. One animal died on day 7, but this was not considered to be treatment-related. The test material did not cause a pain response, corneal or iridial irritation. The eye irritation that occurred had cleared by 48 hours. Based on the Draize scores, the material is not considered to be an eye irritant.

Respiratory Irritation:

No studies of respiratory tract irritation have been conducted with slack waxes (carcinogenic or unknown feed-stock). Inhalation exposure to slack waxes is not expected to occur under normal conditions due to the very low vapour pressures of these substances.

Slack Waxes (Non-carcinogenic Feed-stock)

Read across justification

No dermal or ocular irritation studies have been reported for slack waxes (non-carcinogenic feedstock), but such studies have been reported for refined lubricant base oils, materials similar to the oil entrained in slack waxes (non-carcinogenic feedstock).

Skin Irritation:

One key read-across study (Exxon Biomedical Sciences Inc., 1988a) was identified to evaluate the skin irritation potential of slack wax (non-carcinogenic feed-stock).

In this study, 112 human adults were dermally exposed to 0.2 mL of refined lubricant base oil once a day, four days a week, for four weeks. A challenge phase was conducted where the participants were treated with 0.2 mL once a day, four days a week, for one week. Participants were asked to report any change in dermal effects for two weeks after the end of the challenge week. Irritation was scored following The International Contact Research Group System (3) and the Product Investigations, Inc. scoring method. In this study lubricating base oil was not a dermal irritant based on the small number of slight or mild irritation responses recorded. It should be noted that the exposure period was for 24 hours rather than the 4 hours which is the basis for dermal irritation classification in the EU.

In another primary skin irritation study (NOTOX, 2003a), the intact skin of three male New Zealand albino rabbits was exposed to 0.5 milligrams of paraffin wax under semi-occlusive conditions for 4 hours. Animals were observed for 72 hours, and skin irritation or corrosion was scored by the method of Draize at 1, 24, 48, and 72 hours. At the end of the 4 -hour test period, excess paraffin wax was removed with water. Slight erythema was observed at 1 hour in all three animals which was fully reversible by 24 hours. Therefore, under conditions of the study, paraffin wax is considered not irritating.

Supporting read-across data from studies conducted in rabbits (API, 1982a; 1982b; 1982c; 1982d; UBTL, 1984a; 1984b; 1984c; NOTOX, 2003b; Shell, 1993; CTFA, 1972; CTFA, 1977; CTFA, 1980) indicate that slack waxes (non-carcinogenic feed-stock) are not dermal irritants.

Eye Irritation:

Two key read-across studies (API, 1982e and CTFA, 1980) were identified to evaluate the eye irritation potential of slack wax (non-carcinogenic feed-stock).

In this study, 6 New Zealand White rabbits (3 male, 3 female) had 0.1 mL of dewaxed light paraffinic oil (API 78-9) instilled into the conjunctival sac of their right eye. The left eyes of these rabbits served as treatment controls. Additionally, 3 rabbits (2 male, 1 female) were administered the test material in the right eye and the eyes were rinsed with warm water 30 seconds following exposure. Ocular lesions were observed for at 24, 48, and 72 hours post-exposure and fluorescein dye evaluations employed for each reading. Grading and scoring of ocular irritation was performed according the method of Draize. Rabbits with washed eyes exhibited no irritation through the 72-hour observation period. A single male rabbit in the unwashed group exhibited conjunctival chemosis at the 48-hour observation period. The remaining rabbits showed no signs of irritation through the study period. Based on the Draize scores, solvent dewaxed light paraffinic oil was not considered to be an ocular irritant.

In another key acute eye irritation test (CTFA, 1980), 0.1 millilitres of a 50% paraffin wax in petrolatum solution was instilled into the eyes of six albino rabbits without rinse. The test material was not irritating.

Supporting read-across data from studies conducted in rabbits (CTFA, 1972; BIBRA, 1993d; Elder, 1984) indicate that slack waxes (non-carcinogenic feed-stock) are on irritating to the eye.

Respiratory Irritation:

No studies of respiratory tract irritation have been conducted with slack waxes (non-carcinogenic feed-stock). Inhalation exposure to slack waxes is not expected to occur under normal conditions due to the very low vapour pressures of these substances.

Justification for selection of skin irritation / corrosion endpoint:

One of 20 available studies

Justification for selection of eye irritation endpoint:

One of 8 available studies

Justification for classification or non-classification

Noting that the procedure used in both studies (API, 1986a and Exxon Biomedical Sciences Inc., 1988a) i.e. 24 hour exposure period with an occlusive dressing, was more severe than the 4-hour exposure period with semi-occlusive dressing, slack waxes (carcinogenic or unknown feed-stock and non-carcinogenic feed-stock) do not meet the EU CLP Regulation (EC No. 1272/2008) as a dermal irritant. Based on available data on similar materials, slack waxes (carcinogenic or unknown feed-stock and non-carcinogenic feed-stock) are not expected to be ocular irritants and do not meet the EU CLP Regulation (EC. No. 1272/2008) criteria for ocular irritation.