Leukemia: The price of living close to an oil refinery?
Barregard L, E Holmberg and G Sallsten. 2009. Leukaemia incidence in people living close to an oil refinery. Environmental Research 109:985-990.
Lysekil is one of the largest and most modern oil refineries in Europe. Yet, during the past 10 years, communities downwind of the refinery had twice as many cases of leukemia as would be expected based on the refinery's low emissions.
But, without further research, the study's authors can only guess as to why the rates vary so much from risk estimates. It could be due to the emissions, an unknown factor or chance.
A number of scientific studies have raised concerns over cancer risks associated with living close to a refinery. This is the first study to compile and analyze information about cancer incidence in a large Swedish population who live near an oil refinery.
Refineries release organic compounds that can cause cancer. For example, the chemical benzene is associated with an increased risk of leukemia.
Regulatory agencies set safe exposure levels for chemicals by testing for effects at high concentrations, then, using statistical extrapolation to determine safe exposure levels. This method assumes that if exposure goes up so do effects and if exposure goes down so will effects. But, research is beginning to show that chemicals do not always follow this rule and may cause different effects at higher and lower levels.
Based on the results, the organic pollutant levels in the exposed areas were well below accepted levels and the incident of cancer should not have increased. But actual measurements showed a doubling in the risk for leukemia in the last 10 years.
The scientists note that more studies are needed to determine why the rates varied so much from predictions. Further research could discern if the increased incidence of leukemia is caused by – rather than just associated with – the refinery's emissions or if some other unknown factor is responsible.
Researchers studied seven parishes in the vicinity of the Lysekil refinery on the west coast of Sweden. Two parishes located 2 to 5 kilometers downwind from the refinery were classified as exposed to refinery fumes. Five other parishes that were greater than 7 kilometers away from the refinery were used for comparison.
The average amount of air pollutants in exposed parishes was estimated from air sample measurements provided by the Swedish Environmental Research Institute. The average exposure was similar to that found in a Swedish city with road traffic, except the levels of propene were five times higher.
The number of refinery employees as well as geological and socioeconomic backgrounds of inhabitants in exposed and unexposed parishes were similar in the exposed and unexposed groups. Within these populations, leukemia cases and total cancer incidence from 1975 – the year that refinery was built – to 2004 were retrieved from the Regional Swedish Cancer Registry.
Reference parishes used as control groups had the expected rates of leukemia and other combined types of cancers. In exposed parishes, the incidence of leukemia was 50 percent higher than expected for the past 30 years – 33 cases were found when only 22 were statistically expected. The highest number of leukemia cases was reported in the last 10 years with 19 cases when only 8.5 would be expected.
The oil refinery and the people in the community were made aware of the study's findings.