Researchers used records from a national health-screening programme to investigate cancer diagnoses among workers who had received different cumulative amounts of ionising radiation during medical imaging.
All workers were followed for 15 years. They were classified by their age at the start of the study.
| Cumulative exposure | Age at start of study | Number of workers | Number diagnosed with cancer |
|---|---|---|---|
| lower | under 50 | 2400 | 24 |
| lower | 50 or older | 600 | 30 |
| higher | under 50 | 400 | 8 |
| higher | 50 or older | 1600 | 128 |
Calculate the percentage increase in the proportion of workers diagnosed with cancer in the higher-exposure group compared with the lower-exposure group.
Describe the relationships between age, exposure and cancer diagnoses shown by the data.
Explain why the results and biological knowledge support, but do not prove, the conclusion that ionising radiation increases the risk of cancer.
102 exam-style questions on Edexcel GCSE Biology 5.4 Non-communicable diseases, covering 5.4.1 Interaction of factors in non-communicable disease, 5.4.2 Lifestyle factors and non-communicable disease, and 5.4.3 Treatments for cardiovascular disease. Each one has a worked solution and a mark scheme showing where the marks go.