Filers should be aware of toxic metals and their potential health problems ° Cobalt is present in both stellite and carbide tips while chromium occurs in stellite tips. by Susan Kennedy, PHD, Associate Professor, and Kay Teschke, MPH, CIH, Assistant Professor, University of British Columbia Department of Medicine and Health Care and Epidemiology aw filing is not a new trade. The use of spe- cially hardened saw tips is, however, relative- ly new (that is, within the past 10 or so years in most mills). Some of the metals used in these specially hardened tips may lead to health problems, if exposures are not controlled. This article will describe the results of a study car- ried out in eight B.C. sawmills which looked at metal exposures and possible health effects from these hardened saw tips. WHY WAS THE STUDY STARTED? The study was planned in response to two events. First, we were contacted by saw filers who were concerned about some symptoms they felt were caused by filing room exposures. Second, we learned about four saw tip grinders in a saw manu- facturing plant in Washington State who developed a rare lung disease caused by exposure to cobalt in tungsten carbide (hard metal lung disease). Together, these events suggested that a study may be needed in sawfiling rooms in B.C. The study was carried out by a research team from the University of British Columbia with research grant funding received from the Workers’ Compensation Board. WHAT WAS THE PURPOSE OF THE STUDY? The study had two main purposes: to find out the level of metal exposures in saw filing room (and if so, what specific jobs or tasks had the highest expo- sure), and to take a first look at whether or not there were any saw filers with the kind of lung dis- ease that is known to be caused by exposure to cobalt in tungsten carbide. WHY DO WE CARE ABOUT THE METALS IN TUNGSTEN CARBIDE AND STELLITE? Cobalt is present in both tungsten carbide and stellite saw tips. Chromium is only present in stel- lite tips (and in knife steel and saw steel). In tung- sten carbide, cobalt is the binder for the other met- als. In stellite, cobalt is more closely associated with the other metals (and there is a different binder). The possible health effects from cobalt and chromium exposure are: 1. COBALT ‘HARD METAL’ LUNG DISEASE Workers who manufacture tungsten carbide tools have been studied several times and it is well known that a small percentage of these workers (about 1%) may develop a lung disease called ‘hard metal disease’. This disease is caused by the cobalt in tungsten carbide. It is a disease in which the spongy tissue of the lungs (where the air and blood meet) becomes inflamed and possibly scarred. Although the disease can be treated (by medicines and by removal from the job) sometimes these treatments do not work and the disease can be fatal. For this reason, shops where tungsten carbide tools are manufactured take care to keep cobalt exposure to a very low level. This type of manufacturing is not common and therefore, many doctors are not very familiar with ‘hard metal lung disease’. There have not been many studies of workers who use or sharpen tung- sten carbide tools, so doctors have tended to assume that the disease was only found in manufac- turing workers (not users). Therefore, the report of four saw sharpeners in Washington with this dis- ease was surprising. If a doctor suspects that a worker has hard metal lung disease, she or he may be able to do special tests to confirm this (although sometimes these are not helpful). Unfortunately, most doctors would not be on the lookout for this disease unless the worker specifically told the doctor that he was exposed to tungsten carbide. So, if a saw filer had this disease, it may be diagnosed as ‘idiopathic interstitial pneu- monia’. This is a fancy phrase that simply means that the worker has a lung disease of unknown cause. Hard metal lung disease can occur in a worker who has worked with tungsten carbide for as little as a year or as much as 30 years. In the studies that have been done, it seems that it may be more com- mon among workers who are involved in wet grind- ing processes. Before we started the study, we were not aware of any saw filer who had been diagnosed as having hard metal lung disease. 2. COBALT ASTHMA Some workers who are exposed to cobalt (in many types of jobs) develop a sensitivity to the cobalt that causes them to have asthma. Asthma is a disease of the air passages which can be treated by medicines and removal from exposure (eg. chang- ing jobs). This disease has also been studied in workers who manufacture tungsten carbide tools, as well as in many other industries where cobalt exposure may occur. It seems to affect about 5% of exposed workers. 2 3. CHROMIUM Chromium, which is present in stellite, is known to cause symptoms of irritation if exposure is high. It can also cause ulceration (or holes) to develop in the part of the nose which divides the two nostrils. Our study was able to look for such symptoms. Chromium can be present in several forms and one of the forms of chromium (called hexavalent chromium) is known to be associated with about a ten fold increased risk of lung cancer. As with most substances which may cause cancer, the higher and longer the exposure level, the greater the risk. Our study was not designed to investigate this issue, because, unfortunately, cancer studies require very large numbers of subjects studied over a long peri- od of time. HOW DID WE DO THE STUDY? The study was done in eight coastal mills which volunteered to participate. Seven of the mills used tungsten carbide tips, six used stellite. One used neither. Each mill was visited four times, at least one month apart, in the summer and fall of 1991. At each visit, each filing room worker wore a personal air sampling device to measure for metals, had breathing tests done in the morning and afternoon, and had his work location and task charted every 10 minutes throughout the day. Each worker also answered a detailed and lengthy series of questions about his current health, his past health, and his current and past job. After testing was completed, we analyzed the results to see what the levels were for metal expo- sures, to see if any particular work location or task was more likely to cause higher metal exposures, to see if any workers had obvious hard metal lung dis- ease or cobalt asthma, and finally, to see if any lung measurement or symptom (even if not obviously one of the diseases) appeared to be associated with any exposure or work task. A total of 278 air samples and 73 coolant samples were analyzed for metals, 196 ventilation systems were tested, and health testing was conducted on 118 saw filing room workers. WHAT DID WE FIND? 1. COBALT AND CHROMIUM EXPOSURE LEVELS Generally, exposure levels were low and most of the 278 air samples did not have levels which could be detected for any of the 22 metals tested. There were 62 air samples with measurable cobalt levels, the average cobalt concentration in these was about10ug/m3. The WCB recommended permissable concentration at the time of the study : pS 8/LUMBERWORKER/SEPTEMBER, 1993