Controversial chemical linked to colour blindness

Its use in the coal seam gas industry remains contentious and now a study presented at an ophthalmology congress has found the chemical toluene, to damage the cells of the retina responsible for colour perception.

Toluene is a ubiquitous solvent found in numerous consumer products as well as diesel and petrol. Toluene is also used by some coal seam gas operators to help fracture rock seams to extract gas.

A study of informal workers in Jakarta, which comprise 64 per cent of Indonesia's industrial workers, has found shoe workers exposed to the highest levels of toluene in glues had the highest rate of colour perception impairment.

The study adds to the body of evidence about health risks from industrial toluene exposure. As well as short-term irritant effects, dizziness, drowsiness and euphoria, long-term exposure to toluene has been associated with kidney and brain damage.

Most Australians would enjoy safer working conditions than Indonesia's informal workforce, however everyday activities such as pumping fuel, cigarette smoking, and using glues, stain removers, or nail polish also involve exposure to toluene.

Speaking at the Asia Pacific Academy of Ophthalmology (APAO) Congress in Sydney, Dr Emil Sjahreza, an ophthalmologist who worked at the University of Indonesia at the time of the study, said colour perception checks were performed on 88 men who worked in shoe factories for more than 12 hours per day.

"Interestingly, the toluene levels were still below the recommended safe limit for industry but the men who worked most closely with the glues were those found to have worst impairment of colour perception," he added.

None of the men used any personal protection equipment such as masks with chemical absorbers or gloves. Air samples were also collected from their workplaces which are typically small rooms with poor ventilation.

"Those men who worked directly with the glues were exposed to mean toluene levels six times higher than men who worked in the next room at a different part of the production process. Their cumulative dose of toluene was also four times higher."

He said more than 60 per cent of men in the high exposure group had some degree of colour blindness including red–green, blue–yellow or, more commonly, a colour perception anomaly with no definitive pattern.

Only 23 per cent of workers in the low exposure group were similarly affected.

Dr Sjahreza said many of the workers were unaware of the change in their vision. No other vision problems or risk factors, such as smoking and alcohol consumption, were associated with the colour blindness.

(Source: Asia Pacific Academy of Ophthalmology Congress)