Background cosmic radiation levels in free space are ten times greater than the maximum acceptable levels for individuals who work in radiation environments on Earth.
太空环境下的宇宙射线辐射强度，超过地球上人体承受极限的十倍以上。
2
Cigarette smoke and radiation also produce free radicals.
香烟烟雾和辐射同样会产生自由基。
3
Based on previous research, the researchers hypothesized that radiation from phones would accelerate progression of the disease be-cause other types of radiation cause free radical damage.