To what extent is there a correlation between total number of employees working in nuclear power plant and number of employees getting infected by cancer for three age groups?

"Although September 11 was horrible, it didn't threaten the survival of the human race, like nuclear weapons do." – Stephen Hawking. Despite the heinous terrorism happens across the globe, the destructive power of nuclear bomb has left a scar and fear in every individual of this world.

Since childhood, I have been listening to the nuisance that happened in Hiroshima and Nagasaki in the year 1945 marking the end of World War II. The destructive capacity of nuclear energy was very clear and prominent to me since the early school days.

It was secondary education when the picture of nuclear power and nuclear energy began to change in front of me when I studied about the nuclear energy as a non-conventional source of energy. Despite initial doubts and queries which arose due to the childhood stories of catastrophism, I came across a fact that it is the nuclear energy which is the face of change in providing energy to the mankind. The amount of energy that could be produced by nuclear reaction is unparallel to any other source of energy.

With passing days, the course curriculum became more intense and I started learning in depth concepts of nuclear energy. About two years from now, I have studied that during the nuclear fission reaction which generates the nuclear energy in Physics. Sooner or later, I felt a deep inclination towards the subject. Due to the highly constructive facility that it provides to the mankind, I thought of pursuing higher studies in Nuclear Energy and working in Nuclear Power Station.

However, currently in Biology, I studied about the disease named cancer. Some of the facts have shattered my dream of pursuing a job in nuclear power plant. In the curriculum, I studied that γ - ray causes cancer. The subtle fear which was developed regarding the devastating effects of nuclear energy again filled into my mind because in nuclear fission reaction, the reaction using which nuclear energy is generated, γ - rays are emitted.

To remove the fear and to concentrate on the career, I started doing a few researches. I read a few journals on side – effects of nuclear energy. There were several instances of an increased chance of getting affected by cancer if an individual is exposed to the harmful γ - ray. However, I came across a lot of articles where the preventive measures were discussed which were taken in every nuclear power plant to protect their employees from radiation. To be more confident on this, I read a lot of news journals and articles from which I came across the fact that employees working in nuclear power plant are often getting affected by cancer. However, I could not find any information on the chances of getting affected by cancer for a nuclear plant employee.

To find the answer, I am working on this mathematical exploration so that I can derive some relation on chances of affected by cancer if I pursue my dream job.

The main motive of this investigation is to explore the correlation between the number of employees working in a nuclear power plant and the number of employees getting affected by cancer.

What is the relationship between the number of employees working in a Nuclear Power Station and the number of employees getting infected by cancer during the working period or after retirement for three different age groups – Gr 1: 50 years to 60 years, Gr 2: 60 years to 70 years and Gr 3: 70 years and 80 years?

Cancer 1 is a disease which is characterized by uncontrolled cell division. It results in repetitive division of cell which often causes formation of tumor, cyst, fibroid etc. However, tumors are categorized into two types – Benign and Malignant; Malignant tumors are considered to be cancerous. Cells of malignant tumor or cancerous cells can spread throughout the body through the blood stream and initiate the formation of tumor in any other part of the body. This results in development of pressure on vital organs on where the tumor has originated which leads to organ failure. Tumor also constricts blood vessels at its vicinity resulting in increased heart rate and blood pressure eventually increasing the chances of stroke or heart fail.

There are several causative agents which triggers the cells to divide at an uncontrolled manner. However, in context of this mathematical exploration, radiation is one of the reasons responsible for causing cancer. Radiations like gamma rays, X – rays, etc. are considered to be one of the most eminent causative agents of cancer. These radiations have sufficient ionization energy to trigger the mutagen present in human DNA. On activation of mutagen of any cell, the cell began to divide continuously without maintaining the cell cycle which leads to formation of malignant or cancerous tumor.

From several news reports and scientific research, it is now a clear statement that due to increased emission of greenhouse gas, depletion of ozone layer has caused the harmful ultra violet rays to pass through the Earth’s atmosphere. As a result, cases of skin cancer have increased invariably in the world. This signifies the effect of radiation in causing cancer.

Nuclear power station 4 or nuclear power plant is a power plant which generates energy by nuclear fission reaction. Nuclear fission reaction is performed in a nuclear reactor in which the heat generated by the nuclear reaction is used to convert water into steam. The steam, thus generated is used to run a turbine which generates electricity.

The nuclear fission reaction is accompanied by emission of radiations, such as, α - rays, β - rays, γ - rays etc. Out of which, γ - ray is considered to be the most harmful radiation. The nuclear reactor is constructed in such a way that the leakage of radiation is assured to be null. However, a number of preventive measures in respect to dresses, medical check – up, etc. of employees working in nuclear power plants are taken into consideration. Despite such preventive measures, instances have been noted where radiation has been leaked which has caused severe illness not only to the employees but also to the individuals living in the nearby areas of the power plant. This is because, γ - ray can pass through even inches of metal sheet like lead.

Regression correlation coefficient is a tool to measure the strength of the correlation between the independent variable and the dependent variable. The set of values (x₁, y₁), (x₂, y₂), (x_n, y_n), are used to find the value of r as stated by the formula below

\(r=\frac{n(\Sigma xy)-(\Sigma x)(\Sigma y)}{\sqrt{[n\Sigma x^2-(\Sigma x)^2][n\Sigma y^2-(\Sigma y)^2]}}\)

In the above-mentioned formula, x is the value of independent variable of each observation, y is the value of dependent variable of each observation, xy is the value of the product of the independent and the dependent variable of each observation, n is the number of observation and ∑ denotes the sum of all the observation of the mentioned variable.

By squaring the value of r, the value of the regression coefficient (r²) will be achieved. The value of r² lies between 0 and 1 where 1 signifies maximum correlation whereas 0 signifies null correlation.

Pearson’s correlation coefficient is a tool to measure the strength of the correlation and also the nature of correlation between the independent variable and the dependent variable. The set of values , (x₁, y₁), (x₂, y₂), (x_n, y_n), are used to find the value of as stated by the formula below:

\(\mathfrak{R}=\frac{\Sigma(x-\bar x)(y-\bar y)}{\sqrt{\Sigma (x-\bar x)^2 \Sigma×(y-\bar y)^2}}\)

In the above-mentioned formula, x is the value of independent variable of each observation, y is the value of dependent variable of each observation, \(\bar x\) is the arithmetic mean of all the observations of the independent variable, \(\bar y\) is the arithmetic mean of all the observations of the dependent variable and ∑ denotes the sum of all the observation of the mentioned variable.

The value of R lies between -1 and 1. A positive value of Pearson’s correlation coefficient implies a direct relationship the independent and the dependent variable whereas, a negative value of Pearson’s correlation coefficient implies a indirect relationship the independent and the dependent variable. If the value of the correlation coefficient is close of 1 or -1, it signifies the correlation exists true. On the other hand, if the value of the correlation coefficient is close to 0, it signifies the correlation does not exist.

Chi squared test  is a kind of analysis which predicts the existence of any correlation between an independent variable and a dependent variable. The Chi squared value of any given set of data is firstly calculated. Now, based on the type of data, for example, paired data or independent data, the Chi squared value is checked in the Chi squared table which further predicts the existence of any correlation.

The formula of Chi squared value is given below

\(x^2 \text{ value} = \sum \frac{(O_i - E_i)^2}{E_i} \)

Here, is the observed value, E_i is the expected value, ∑ denotes the sum of all the observation of the mentioned variable.

Now, the Chi squared value is checked in Chi squared table which predicts the existence of any correlation. The Chi squared table is shown below

It is assumed that there does not exist any correlation between the number of employees working in a Nuclear Power Station and the number of employees getting infected by cancer during the working period or after retirement for three different age groups – Gr 1: 50 years to 60 years, Gr2: 60 years to 70 years and Gr3: 70 years and 80 years.

It is assumed that there is a correlation between the number of employees working in a Nuclear Power Station and the number of employees getting infected by cancer during the working period or after retirement for three different age groups – Gr 1: 50 years to 60 years, Gr2: 60 years to 70 years and Gr3: 70 years and 80 years.

A data sheet has been prepared based on several news articles, reports and surveys in different nuclear power plant across the globe. It has been possible to record the data of number of employees got infected by cancer during their tenure of service because of the health insurance policy that the company offers to all its employees. Similarly, the health status of the retired employees has been achieved from the health benefit that the company offers even after retirement.

The employees working in nuclear power plant has been categorized into three groups to illustrate the correlation in a proper and intensive way. It has been studied that immunity against cancer is more in young age than that of the elder. However, there are lot of exceptions; mutagen is activated in elder people with very less exposition to radiations than that of others. On the other hand, it has been observed that an individual at a young age has been exposed to cancer causing radiation, however, the cancer has been observed at a very later period of his life. Thus, considering the strength of immunity in an individual, the age groups are made accordingly.

Sample Calculation

Percentage of Infected Employee \(= \frac{34}{326}=10.33\)