Asphalt Health Hazards

ASPHALT HEALTH HAZARDS

The research world-wide on possible adverse human health hazards following exposure to bitumen, is limited. Most investigators question the possible links between bitumen and cancer. There is a great deal of uncertainty regarding the degree of exposure necessary to cause such health effects.

Inhalation

Inhalation of bitumen fumes may cause irritation of the respiratory tract. After long term exposure to high concentrations of fume, chronic bronchitis with reduced (PEF) and, possibly, other respiratory disorders may result. It is uncertain whether the irritant effect from inhalation of fumes also may influence the gastrointestinal tract. There is little evidence that lung cancer can result from inhalation of bitumen fumes. Where cut-back bitumens are handled, acute or longer-term exposure to fumes of the carrier material (white spirit, gas oils or kerosine) may result in irritation to the respiratory tract or "organic so/vent syndrome". Spraying of emulsions can result in the generation of a mist. Whether this presents a hazard will depend on particle size but it is unlikely to be within a respirable range (< 5 um). In confined vapour spaces above heated bitumen in storage tanks, hydrogen sulphide may present a potential hazard.

Ingestion

The physical nature of bitumens and derivatives makes their ingestion unlikely during normal use. However, in the event that accidental ingestion does occur, some irritation of the gastrointestinal tract may arise and result in vomiting with the potential associated danger of aspiration.

Aspiration

Aspiration of liquid into the lungs, either directly or as a result of vomiting after ingestion, is only a possibility with cutback bitumens and emulsions and will not occur with other bitumens and derivatives. Aspiration could give rise to a rapidly developing and potentially fatal chemical pneumonitis depending on the other components present with the bitumen.

Skin Contact

Most bitumens and derivatives are handled hot, and the main danger is from thermal burns.
Cutbacks may sometimes be handled at lower temperatures where prolonged and repeated contact may occur. In addition to causing skin irritation, it would be prudent to assume that such contact may present a potential carcinogenic hazard, particularly under conditions of poor skin hygiene. The situation may be exacerbated by ultraviolet rays in sunlight.
Exposure of the skin to high concentrations of bitumen fumes may also cause skin irritation since there may be condensation onto the skin.

Eye contact

A hot bitumen splash may cause serious eye injury. Direct contact with cutback, emulsions and small particles of cold hard bitumens may cause eye irritation.
Irritation of the eyes from exposure to bitumen fumes is also reported among asphalt workers. Although this rarely causes any severe damage to the eyes, it may be a considerable problem to the asphalt workers.

HEALTH ASPECTS ASSOCIATED WITH SPECIFIC APPLICATIONS

Hot Mixes

Exposure to fume can occur during loading, transport and application of the finished product. Here it is essential to control aggregate temperature such that the product is not overheated. (The 1990 EAPA conference recommends that 160°C should be the maximum production temperature for normal products). During the application procedure there is a limited exposure to fume, but again this can be minimized by ensuring that the initial product is not overheated.

Surface Dressing

Exposure to fume occurs in the immediate vicinity of the spray system (normally a purpose built tanker). The main operatives at risk are the spray bar operator and the driver of the aggregate distributor. Modern equipment trends either eliminate the need for a spray bar operator, or provide a protective ventilated enclosure. In the case of the aggregate distributor driver, modern trends in equipment provide an enclosed ventilated environment:
Where older equipment is used an air hood can be used by both spray bar operative and aggregate distributor driver.
In addition cleaning equipment after spraying has a potential for skin contact.

Recycling

Rejuvenating agents which may be high in PACs are sometimes used in conjunction with asphalt recycling. Such agents would not normally be classified as bitumens and appropriate advice should be sought. The old asphalt layer may contain coal tar, a coal tar creosote or materials such as reclaimed tyre rubber or PVC, which when heated produce hazards associated with the fumes of these products. A fume hazard may exist in hot recycling processes both in situ and in plant, where overheating of the old asphalt pavement can cause fumes. In cold recycling, emulsion sprays may be generated when unenclosed spray systems are used as part of the mixing processes.

Roofing

Exposure to fumes land sometimes mineral dust) may occur during felt manufacturing processes especially if ventilation is poor. The major hazards associated with felts application are skin burns and adverse effects from fume exposure; the highest exposure takes place when heating/handling the hot ( > 200°C) mopping bitumen.
Liquid roofing products are manufactured, handled and layed at moderate or ambient temperatures. The health hazards in these situations are associated with the use of solvents with most formulations.

Industrial applications

Industrial applications are varied and cannot therefore be covered by general statements. The health hazards will depend upon the procedures involved, e.g.

- Lining and waterproofing operations may be considered as roofing or paving, depending upon the technique.

- Flooring requires handling of hot mastic asphalts that are often laid by hand in enclosed areas. The hazards are of the same type as those encountered in using hot bitumen mixes, but the potential exposure to fumes is higher because of the use of much higher
temperatures (around 250°C), sometimes with reduced ventilation. The bitumens are usually hard grades.

- Protective coating may give rise to concern when applied diluted in a solvent which often contains aromatic hydrocarbons.

- Paper or cardboard impregnation is carried out at moderate temperature and the end product is usually applied at ambient
temperature.