Good news from Cobalt study
Long-term exposure to cobalt does not increase the risk of cancer among workers at Seco and other companies in the Sandvik Group. That’s according to a large scientiic study published in the December issue of the Journal of Occupational and Environmental Medicine.AN INTERNATIONAL STUDY covering more than 32,000 individuals in five countries and spanning many decades has shown that long-term exposure to cobalt, which is mainly used in the hard metal industry, does not increase the risk of lung cancer.
“Smaller studies had previously shown an increased risk of cancer,” says Professor Håkan Westberg from the Department of Occupational and Environmental Medicine at Örebro University, one of the researchers behind the Swedish part of the new study. “But these lacked key parameters such as exposure based on cobalt concentrations in the air over time and smoking habits.”
Cobalt concentrations in the air have been significantly reduced over time. Today, all the Swedish companies involved in the study have levels generally well below the relevant limits.
“So, how can we use the results from this ‘negative’ study?” asks Westberg. “We started out looking at the cohort with the highest exposure, but we didn’t find any excess risk in it. From that, we calculated the approximate cobalt air-concentrations to which you could be exposed during your working life without risk of lung cancer. Current exposure levels at the Swedish companies involved in the study are at or below this level.” However, Westberg adds that it’s important to continue the monitoring of exposure levels as well as prevention and preparedness to prevent the occurrence of other cobalt-related ill-health.
Seco takes a very positive view of the study. The company’s global environmental coordinator Maria Blomqvist explains, “Seco is a company that wants to rely on facts. We want to chart the real situation so that we can respond accordingly.”
The company has worked for decades to ensure a good working environment for its employees and has taken action to reduce their exposure to substances such as cobalt.
“Of course, it’s now good to find out that nobody in our factories needs to be afraid of dying from cancer or other diseases because of their work,” Blomqvist says.
The legal Swedish limit for cobalt is 0.02 milligrams per cubic meter (mg/m3). Seco has an internal limit of 0.01 mg/m3 and its target is to get it down to 0.005 mg/m3 .
“In fact, we’re almost there,” Blomqvist says.
Westberg considers that Seco can take a lot of the credit for the fact that the large study took place at all. “It all started with us wanting to carry out an occupational health study in Fagersta,” he says. “But, interest was gradually awakened throughout Sandvik and also ultimately in the International Tungsten Industry Association (ITIA).”
DIGGING DEEP INTO THE PAST
THE SWEDISH COMPONENT of the cobalt study involved studying over 15,000 people who worked at Sandvik’s plants in Fagersta, Gimo and Västberga in Stockholm. Personnel records at Fagersta stretched back to the 1920s, while at Gimo and Västberga records went back to the 1940s. Details of names, personal identity numbers, duration of employment and occupation were correlated with mortality and the cancer register of the Swedish National Board of Health and Welfare. The results were then compared with the mortality and morbidity rate among the general population and the local population in Västmanland, Uppland and Stockholm.
Researchers also looked at what is known as the latency period – the time between exposure and onset of a disease – and eliminated those who had contracted lung cancer so rapidly after exposure that the cause must have been something other than cobalt. They also had access to historical measurement data on cobalt air concentrations in the plants.
“When it comes to smoking habits, it was a bit more difficult,” says professor Håkan Westberg at Örebro University, one of the researchers behind the study. “We sent out smoking behavior questionnaires to living members of the cohort and to relatives of those who had died since 1991. However, the response rate was low.”
The results show that both an excess mortality and increased morbidity rate overall from cancer, cardiovascular disease and chronic obstructive pulmonary disease are strongly associated with short-term workers.
“Mortality was significantly higher for the entire cohort studied, especially for lung cancer and for cardiovascular disease and respiratory disease,” says Westberg. “The excess mortality was strongly associated with short-term workers, that is, those employed for less than a year. Where lung cancer was concerned, we noted a reducing risk with increasing exposure since the employment period was used as measure of exposure. The use of different exposure criteria based on measurement data produces the same pattern. In other words, increased risks at low exposure levels but not at high ones.”
The results are based on comparisons with the general population, and here differences, especially in smoking habits, can affect the results. The smoking surveys carried out did not show any significant differences between different occupations over time.
“We, therefore, also carried out analyses in which we compared lung cancer morbidity in different exposure groups within the cohort exposed to cobalt. We were able to establish that increased exposure did not seem to result in increased risk,” Westberg says.
