I am not a doctor, nor a physicist, nor any other qualified person to discuss radiation safety for others. I am merely explaining my own risks using my own sources. Keep that in mind.
Cancer occurs when cells in the body are damaged in such a way that they their genetic code is altered allowing them to uncontrollably reproduce. This damage can come from the environment and from errors in how DNA is rewritten.
Current Scientific Consensus (what the majority of scientists agree upon based upon their research and data):
1. Cancer risk rises with respect to dose.
2. There is no dose rate where the risk of cancer (from the dose) is zero.
3. Determining risks from doses less than 100 mSv is statistically difficult.
December, 2008. Williams D. Radiation carcinogenesis: lessons from Chernobyl. Accessed online January, 23 2015 at http://www.ncbi.nlm.nih.gov/pubmed/19956182
The dose of a dental x-ray 5 μSv
The majority of small check sources are less than 10 μSv/hr
The dose of chest x-ray averages 100 μSv
The dose of a CT chest scan averages 7000 μSv
The dose of a CT chest scan averages 4,000,000 μSv
Accessed online January, 20 2015 at http://hps.org/documents/Medical_Exposures_Fact_Sheet.pdf
What are the risks of cancer from any source?
Risk of developing 1 in 2
Risk of dying from 1 in 4
Risk of developing 1 in 3
Risk of dying from 1 in 5
September 24, 2014. Lifetime Risk of Developing or Dying From Cancer. Accessed online January, 23 2015 at http://www.cancer.org/cancer/cancerbasics/lifetime-probability-of-developing-or-dying-from-cancer
A third to half of us will get cancer in our lives. My sources are only a VERY tiny contributor to my risk.