SUMMARY. Hot tar burns mainly occur in workers in the paving and roofing industries. They present a difficult clinical problem owing to the adherence of material to the underlying skin. In the past, in Lebanon, diesel oil was widely used in the construction business in cases of tar burns, with rapid removal and excellent results. Because of the unavailability of solvents, diesel was applied in a recent case described in this paper. There was no further damage to the underlying burn. A review of the literature revealed that diesel has never been reported as a solvent for tar burns. Further research is recommended.

Introduction

Burns due to hot tar present a difficult management problem because tar is difficult to remove without causing further injury to the underlying burn.
Dickson et al. reported that in the Bradford Football Stadium fire, falling molten bitumen was the cause of injury in some patients who substained mixed-depth scalp burns. Deep dermal or full-thickness burns of the scalp were tangentially excised and skin grafted.' In a nine-year review by James and Moss of 24 patients with such burns, sixteen required operative treatment to achieve healing; no secondary reconstructive procedures were performed. They suggested the following management principles:

• cool the bitumen continuously with cold water until it hardens, in order to dissipate retained heat
• leave the bitumen intact except around the eyes
• deroof tense blisters

Case report

Fig. I - Tar burn before diesel treatment. Fig. 2 - Immediately after tar removal with diesel oil and body shower.

The major health problems in the roofing trade are caused by the use of coal-tar pitch products. Severe eye and skin irritations are frequent among roofers.' Contact burns due to thermoplastic road paint also occur; this is used at similar temperatures to tar and bitumen, and spillage on to skin causes similar contact burns. Most of these occupational burn injuries can be avoided by observing the manufacturer's recommendations about the wearing of protective clothing.
Tar or asphalt, a residue of petroleum refining, is composed of paraffinic and aromatic hydrocarbons and heterocyclic compounds containing sulphur, nitrogen and oxygen. It becomes liquid when heated to 93 'C. However, it is often heated to over 232 'C when it is used for roofing and paving. At these temperatures, molten tar causes deep burns. Two-thirds of these burns involve 3 to 5% of the body surface, and only one-third involve 10% or more.
Ng D. et al.1 reviewed work-related burns between July 1989 and May 1990 (193 patients, tar and asphalt burns representing 9.3%). Between July 1984 and 31 December 1991, 27 consecutive patients were admitted to the Grady Memorial Hospital Burn Unit requiring treatment for hot tar burns. This group represented 1.4% of all admissions to this burn unit. Ninety-six per cent were males. The mean age was 33.7 years. The mean burn extent was 13.1% of total body surface area. Burn topography centred on the upper extremities and hands. Forty-one per cent of the patients required a surgical procedure for their burn. The mean hospitalization time for survivors was 16.6 days. The survival rate was 92.6%. Both the patients who died had large burns and/or pre-existing medical problems. Hot tar burns occur in predictable circumstances and appear to be preventable. They account for only a small fraction of all admissions.' In this case report the patient was a young male who sustained a 10% surface burn involving the face, left forearm, and hand.

Fig. 3 - Before treatment Fig. 4 - After removal of tar.

A review of the literature shows that various substances have been used in the management of tar burns, including mayonnaise," butter," and the surface acting agent polyoxyethylene sorbitan (Tween 80, Sigma, St Louis, Mo) or polysorbate (Sigma), either by itself or in combination with an antibiotic ointment (neomycin sulphate). These have been found to be safe and effective means of tar removal.
Liquid solvents such as kerosene, gasoline, acetone and alcohol have been found to be generally ineffective in removing tar and can damage local tissues, occasionally producing systemic toxic effects due to absorption. Neosporin (polymyxin B sulphate/neomycin sulphate/gramicidin) cream has been found to dissolve tar, thereby facilitating removal, Its emulsifying agent, polyxyethylene sorbitan has excellent Iyophilic and hydrophilic properties and is thus a very effective non-ionic surface active agent. The polysorbate lowers surface tension and promotes micelle formation at the cell surface, thus clearing the bond between the cell surface and the adherent material. Because of the polysorbate's hydrophilic action, the emulsified tar can be washed off with water. Neosporin ointment (polymyxin B sulphate-zinc bacitracin-neomycin sulphate) with a petrolatum base also dissolves tar but is less effective than the cream, which has a polysorbate base. Polyoxyethylene 20 sorbitan mono~olcate (Tween 80, the 80 referring to the average molecular weight of the polyethylene glycol polymer) is another readily available polysorbate that serves as an emulsifying agent and a dispersant in cosmetics and coal tar ointment used for treating skin disorders.
An anecdotal report from an old family friend who works in the construction business suggested that diesel oil was used safely and efficiently by workers in that industry. There is no evidence in the literature regarding the use of diesel oil in the removal of adherent dried tar after bitumen burns. 1 used diesel oil in my patient, and it proved highly effective and safe.

Fig. 5 - Before treatment. Fig. 6 - After removal of tar.

Tar burns involving more than 10% of the body surface area are likely to be the most serious, requiring intravenous fluid resuscitation and a petrolatum-based ointment applied to the burn in the initial stages.
The following recommendations represent a summary of the comments received from numerous physicians involved in burn care, both in the United States and elsewhere, in response to an inquiry from the United Union of Roofers, Waterproofers and Allied Workers, as directed by their International President Roy E. Johnson, regarding the initial treatment of hot bitumen burns.

1. Immediate on-site care

   • Cool the bitumen with water (preferably cold) to limit tissue damage and prevent further spread of the bitumen

   • Cooling should continue only until the bitumen has hardened and cooled. Body hypothermia must be avoided

   • Adherent bitumen should not be removed "in the field" but only at a medical facility by qualified personnel

2. Definitive care by medical personnel

   • Bitumen adherent to skin blisters after cooling should be removed with the blister epithelium in th e course of initial cleansing and debridernent

   • Bitumen adhering to unblistered tissue should in general be left in place and covered with a liberal application of a petrolatum or animal-fat-based material (petrolatum per se, lanolin, mineral oil, and antibacterial ointments were used by various respondents to the questionnaire). Antibiotic-containing ointments, which may limit bacterial proliferation on the burn, were most widely used by respondents

   • The adherent bitumen should then be dressed and the dressing removed on a daily or more frequent basis. Repeated ointment and dressing applications