Amorphous glass toxicity 1

The toxicity of crystalline silica is well established and the toxicity of glass fibres is fairly well know. However the toxicity of amorphous glass dust is less investigated. I was given a copy of Karl Kruszelnicki’s book “Science is Golden” for Christmas. The chapter ”A Glass Act” discusses the myth “ground glass kills you” :  “Victorian authors have clever plots in which some of their fictional characters used this mysterious ‘ground glass’ to surreptitiously kill off unwanted relatives, in order to get their grubby little hands in the family fortune” … “In Victorian time the victim after ingesting the ground glass’ would die slowly and very painfully, thereby giving the murderer much satisfaction”.

I must have gone to a very Victorian primary school as I can still remember heated debates about putting ground glass in the teacher’s sandwiches and whether the teacher would detect the glass. Karl refers to a 1642 writer and physician Sir Thomas Brown who fed ground glass to dogs and debunked the myth.

In Australia some 1500 tons of plate glass used to be recycled, but this stopped and an enterprising person saw an opportunity to grind the glass and classify it by size. Different grades could be used as fillers in polymers and as a special shot blasting abrasive. The glass would not corrode like iron beads and could be used to remove the paint on aircraft without damaging the aluminium. However the company needed to produce an MSDS (Material Safety Data Sheet) to market the product. I was asked to review the toxicity of glass dust to assist the MSDS production. All my research pointed to one single paper:

• Gross, P., M. L. Westrick, et al. (1960). “Glass dust. A study of its biological effects.” A.M.A. Archives of Industrial Health 21: 10-23.

Gross et al. found that dust produced by firing glass powder at a steel plate did not produce any fibrosis in rat lungs, but did find that when rats were fed a diet laced with glass dust, they loss weight when the diet got to 50% glass. Imagine a pizza with a glass dust and cheese toping – it would have to be unappetising, so its not surprising the rats lost weight.

The glass dust is very sharp – its that characteristic that makes it good for abrasive blasting, but the microscopic knives are so small, they do not have the capability to cut. In the lung, the glass is biologically inert, or if the particles are small enough, dissolve in lung tissue. I did predict that if the glass powder got under the seal of respirators, it could act as mechanical irritant – this proved to be so.