<< Back to Silica, Crystalline

Disclaimer: This is not DOL or OSHA controlled material and is provided here for reference only. We take no responsibility for the views, content, or accuracy of this information.


by
David F. Goldsmith, PhD
Public Health Institute
 
The National Conference to Eliminate Silicosis March 23-25, 1997 in Washington DC enjoyed a splendid turnout of over 600 attendees. In my opinion, the conference attention on silicosis to the exclusion of discussion of other silica health effects was very shortsighted . However, I was delighted by the opening remarks by NIOSH Director, Dr. Linda Rosenstock, who pointed out that we now know that silica exposure is a risk factor for several "new" conditions, and that deliberations should be expanded to consider other health problems such as cancer, autoimmune diseases, nephritis and other kidney diseases, and tuberculosis (TB).

What is the evidence for these other conditions? Last month the International Agency for Research on Cancer (IARC) changed the classification of silica from 2A (probable human carcinogen) to 1 (known human carcinogen). The change to IARC Type 1 means that occupational silica dust exposure is considered like other known human carcinogens such as asbestos, vinyl chloride, radon daughters, smoking, and DES. It means that companies are likely to change their Material Data Safety Sheets (MSDS), that workers need to be informed, and that where there are alternatives to silica (such as sandblasting) that they need to be sought out. The change in IARC status does not mean that the controversy about carcinogencity is over, but it does mean that the evidence is sufficient to convince a group of IARC experts that silica increases the risk of lung cancer. Furthermore, it goes a long way to meeting the criteria for causation we use in epidemiology. There is other evidence to suggest that silica is linked to stomach cancer, lymphatic cancers, and skin cancer, though the IARC focus was on pulmonary malignancies.

The other health effects are not "new," but we now have good epidemiology studies of recent vintage showing that silica exposure (with and without silicosis) is linked with several autoimmune conditions which previously there were only case studies: rheumatoid arthritis, scleroderma, Sjogrens' syndrome, and lupus. There is also accumulating epidemiology evidence that occupational silica exposure is linked with kidney diseases such as nephritis and end-stage renal disease.

With a narrow focus on silicosis, we tend to overlook serious conditions that often accompany silicosis--silicoTB and cor pulmonale (enlargement of the heart muscle). Although these two secondary effects of silicosis are declining in the U.S. (as is silicosis), they remain killers of relatively young workers in developing countries and in China and former Soviet Union. Sadly we also must acknowledge the epidemic of acute and accelerated silicosis that descended upon Mexican workers in the Midland-Odessa, Texas area in the early part of the 1990s, some 60(!!) years after the Gauley Bridge disaster. These men were vastly overexposed to silica, without any protection, in several oil pipe sandblasting operations, and they have many of the autoimmune ailments as well as fatal silicosis.

Thus, the silicosis prevention we all hope to achieve should include these other diseases: cancer, autoimmune illnesses, kidney diseases, and TB. Furthermore, the employees we need to communicate with about this hazard must receive information in languages of the workers at risk, not in English only.

David F. Goldsmith, PhD
Public Health Institute
2001 Addison Street, 2nd Floor
Berkeley, CA 94704-1103 USA