This is the final paper for Academic English Science 311: Write & Review Scientific Reports class at University of Calgary. This is for your references only and please do not copy my work and submit as your own. You can read my other paper for this class here.
by
Sanuja Senanayake
Dr. S1234567
Science 311
12-April-2012
[Word Count: 1879]
Introduction
It is human nature that we identify and categorize the root causes of diseases to discover suitable treatments and preventive measures, but the advancement in cancer epidemiology has been an uphill battle for the scientific community. Over the last six years, the uranium mining industry has boomed as a result of rising global demand for energy resources (Solea et al. 2011). Although uranium is an economically viable option, scientists have raised criticisms regarding health concerns caused by radioactive decay.
Humans are exposed to uranium during its mining, processing, fabrication, transportation, and disposal. Within these stages of uranium usage, it is critical to pay attention to the health of those who work in the frontline uranium ore mining industry. There are growing concerns about pollutants in the underground mining environment. The occurrence of lung cancers among uranium miners has been specifically highlighted by several research groups. This is because most research projects regarding the prevention and treatment of cancers among miners have been centered on radon and radioactive gas exposure in underground work sites. However the issue of whether or not uranium carcinogenetic radon is the root cause in the high rate of cancers among miners has been controversial (Boice et al. 2010). This paper will address the difficulties in establishing a strong link between radon exposure and cancers among uranium miners and fabricators because of the epidemiological and anthropogenic variables associated with the study subjects.
Questionable classification of uranium as a human carcinogen
Due to a lack of clear evidence, more research has to be performed in order to classify uranium as a human carcinogen. Unenriched uranium in the environment, such as the roll front ore deposits, are weakly radioactive unless the deposited uranium undergoes rapid oxidation. However, during the mining process, uranium ore deposits are extracted using oxidizing chemical reactions, which makes the material more radioactive (Britannica 2010). This extracted uranium has been used on mice to demonstrate its carcinogenic behaviour in several studies (Domingo et al. 1989). But these laboratory results were obtained using a highly controlled set of subjects, eliminating the anthropogenic factors, as opposed to the uncontrolled subjects used in studies involving uranium miners and fabricators. For example, the records of cancers among the Elodorado uranium mining community had to be readjusted according to tobacco smoking habits and family history (Lane et al. 2010). While the research analysis strongly suggested that there was a connection between the high rate of lung cancers as a result of radon decay product (RDP) exposure, Lane and his peers did not specifically highlight the impact of these adjustments on the overall conclusion of the study. The researchers (Lane et al. 2010) had often depended on the information voluntarily given by the subjects during verbal interviews. Therefore, the information on behaviour and migration could have been easily misrepresented. Hence, the adjustments made to the study based on human habits were questionable.
The reliability of the data could have been improved using various data collection techniques. For instance, the data accuracy could be improved if the miners were monitored from an early stage of employment. To counter the anthropogenic issues on epidemiology, some scientists have relied on the long term data collected by uranium companies (Kulich et al. 2011). These data were somewhat more reliable than the data from interviews, because mandatory health information was collected from the first day of employment. However, the data could be manipulated, since it was collected by the mining company, which is a biased party, with investments in the industry.
Another complication is the variation among the ethnicities, genders, and economic status of the subjects (Boice et al. 2010). Boice and his group had concluded that uranium should not be classified as a major human carcinogen because it is not highly radioactive, and argued that studies on the cancers of uranium miners were flawed, as most researchers did not properly account for anthropogenic factors. This is a critical observation because none of the scientists who supported the idea that RDP exposure caused cancers, such as Kulich and his team, were able to conclusively rule out all other risk factors, such as ethnicity, gender and economic background. While one can argue that the uranium industry may be involved in preventing governments from classifying uranium as a carcinogen, these opposing scientific views are the main reasons behind why it is a difficult task to prove that RDP has a direct relationship to cancers.
Cancer rates among uranium workers
To prove that RDP has a direct link to cancers, in Grants, New Mexico, scientists separated subjects into several different categories (Boice et al. 2010). For critical analysis, subjects were separated based on ethnicities, economic and social backgrounds, and their habits concerning tobacco smoking. This method, in contrast to studies which only separated the tobacco smokers from non-smokers, helped Boice and his team analyze specific types of cancers, depending on the background of each subject. The underground mining workers had a higher rate of all cancers than the above-ground workers, who were involved in the milling and fabrication of uranium. In contrast, these underground miners largely had different variations of lung cancers, compared to their counterparts that worked in uranium mills and manufacturing plants, who suffered from other types of cancers. However, researchers did not provide details of the different types of lung cancers. Hence, it is impossible to review the data, which may be useful to future researchers.
Even though underground miners had a large rate of lung cancers, they were consisted of a large group of men who were known to smoke tobacco, and came from an ethnic background with a high rate of lung cancers, as identified by health authorities. Most of the underground workers were lower middle class Caucasians who were known to smoke tobacco at a much higher rate than their counterparts, the above-ground workers, who were Native American and Hispanic. This, along with the fact that the non-smoking female population in the region who were not miners did not experience an increase in lung cancer, led to the conclusion that it was highly unlikely that RDP exposure can lead to an increase of any other type of cancer other than lung cancers. However, by doing so, this team of scientists also failed to provide strong results for or against the argument that RDP causes cancers. They should have either eliminated the RDP as a cause of cancers, or stated that RDP caused only lung cancers. In addition, they failed to point out that their study might have provided evidence for the concept that the underground enclosed mining environment was probably the root cause of lung cancers. One reason for this may be that Boice and his associates did not find enough data on the rates of airborne radioactive radon levels inside the mines; this makes it harder to prove or disprove that the radon from uranium decay itself was the reason for the high rate of lung cancers. Low levels of radioactive particle exposure may have given a completely different result than high dosages of RDP exposure, because typically, the concentration levels and exposure periods of any carcinogen play a direct role in the occurrence of cancers. In addition, the collected data include only the concentration levels of arsenic. This restricted the information that was available for scientific studies.
In a separate study in Scotland, scientists were able to link the rate of cancers to economic backgrounds (Wood et al. 2003). Subjects from affluent areas showed fewer cancers and higher cancer survival rates than economically-deprived areas of the population. Considering that the miners in the Grants study were economically-deprived, and the lifestyle of those miners were that of the lower middle class, their economic backgrounds may have also promoted the spread of cancerous diseases. It is important to highlight the fact that the rate of stomach cancer has actually decreased in that population over the years (Wood et al. 2003). Thus, it appears that working and living near uranium mining, milling, and fabrication operations does not increase the possibility of developing a cancer.
Increase in lung cancers as an indication of carcinogenicity of RDP
The possible link between lung cancers and RDP exposure was studied using over three thousand people, which made it the largest study yet on lung cancer due to radon exposure (Leuraud et al. 2011). This particular study included subjects from several European mining sites, which provided the researchers with miners from diverse demographic regions, and also included both smoking and non-smoking miners. The data that was adjusted according to smoking preferences suggested that radon exposure significantly increases the rate of lung cancer. When radon exposure is combined with tobacco smoking, it significantly increases the risk of lung cancers, compared to tobacco smokers who do not work or live near the mining operations. Another study strongly suggested that lung cancers are closely associated with levels of airborne dust in the enclosed mining environment, rather than just exposure to radioactive radon in low concentrations (Kulich et al. 2011). Kulich’s study compared the arsenic dust concentration records from the mining company against respective cancer rates. Even though arsenic dust concentrations were minimal in the mines, enclosed underground environment with high concentrations may have increased the exposure levels compared to exposure outside of the mines. The company kept records of arsenic dust provided an another insight. They may had suspected a connection between arsenic and high rate of cancers.
Cancer rates in uranium mining communities
The rates of leukemia, breast and stomach cancers among mining communities are almost the same as those of the general population. There is no significant difference in the rate of leukemia among children born in mining communities compared to those residing in non-mining communities. Although, breast and lung cancers are associated with uranium mining, there was no significant increase in these types of cancers among female miners (Leuraud et al. 2011). Many of the studies on cancers related to uranium radon exposure have concentrated on lung cancers, rather than on all types of cancers, creating somewhat of a scientific bias (Kulich et al. 2011). Because cancers such as leukemia among children born in the region have often been overlooked in most of the above studies, the studies themselves are flawed. Any research group attempting to objectively determine the impact of the mining industry on health should include all types of cancers, rather than just focusing on lung cancer.
Conclusion
It is debatable whether radon exposure alone in uranium mining environments can directly increase the rate of cancers; even lung cancers among uranium miners may be caused by a combination of several other carcinogenic compounds and anthropogenic factors. However, the combination of tobacco smoking with underground RDP exposure significantly increases the rate of lung cancers. There is no significant increase in cancers among uranium millers and fabricators, compared to those who work underground. These contradictions are some of the few strong reasons that, in most uranium-producing countries like Canada, it is not listed under the high-risk carcinogenic materials category. There is a lack of direct evidence to support or refute the claim that radon exposure can causes cancers. Until more large-scale comprehensive studies with consistent data are conducted on this subject matter, the miners should be protected by proper employment regularities, as well as appropriate safety equipment.
References:
Research Papers
Boice JD, Mumma MT, Blot WJ. 2010. Cancer incidences and mortality in populations living near uranium milling and mining operations in Grants, New Mexico, 1950-2004. Radiation Research. 174(5):624-636. doi: 10.1667/RR2180.1
Domingo JL, Paternain JL, Llobet JM, Corbella J. 1989. The developmental toxicity of uranium in mice. Toxicology. 55(1-2):143-152. doi:10.1016/0300-483X(89)90181-9
Kulich M, Rericha V, Rericha R, Shore DL, Sandler DP. 2011. Incidence of non-lung cancers in Czech uranium miners: a case-cohort study. Environmental Research. 111(3):400-405. doi: 10.1016/j.envres.2011.01.008
Lane RSD, Frost SE, Howe GR, Zablotska LB. 2010. Mortality (1950-1999) and cancer incidence (1969-1999) in the cohort of Eldorado uranium workers. Radiation Research. 174(6a):773-785. doi: 10.1667/RR2237.1
Leuraud K, Schnelzer M, Tomasek L, Hunter N, Timarche M, Grosche B, Keruzer M, Laurier D. 2011. Radon, smoking and lung cancer risk: results of a joint analysis of three European case-control studies among uranium miners. Radiation Research. 176(3):375-387. doi:10.1667/RR2377.1
Wood R, Fraser LA, Brewster DH, Garden OJ. 2003. Epidemiology of gallbladder cancer and treads in cholecystectomy rates in Scotland, 1968-1998. European Journal of Cancer. 39(14):2080-2086. doi:10.1016/S0959-8049(03)00370-8
Review Papers
Solea KC, Coleb PM, Featherc AM, Kotzed MH. 2011. Solvent extraction and ion exchange applications in Africa’s resurging uranium industry: a review. Solvent Extraction and Ion Exchange. 29(5-6): 868-899. doi:10.1080/07366299.2011.581101
Instructor Approved Sources
Uranium processing. 2010. Encyclopaedia Britannica Ultimate Reference Suite[CD-ROM]. Windows DVD Edition. Chicago: Encyclopaedia Britannica. Windows 7 Professional.