Ionizing radiation has proved to be most valuable, for example, in clinical diagnosis and radiotherapy. However, inadvertent exposure to relatively high doses of ionizing radiation is capable of injuring and killing cells, inducing mutations, producing developmental abnormalities in fetuses exposed in utero, or even producing latent cancers. On earth, it is impossible to escape exposure to radiation. Cosmic rays bathe the earth continuously, as do terrestrial concentrations of radionuclides, such as radon gas. The two constitute natural "background" radiation. Few humans in developed countries escape diagnostic X-rays, and many require radiotherapy as a potential cure for various types of neoplasia. The "early" injurious effects of radiation appear only when certain cumulative levels of exposure to radiation have been exceeded. However, the later appearing consequences may have no thresholds; hence, the public's concern about the possible carcinogenicity of even low-level exposures.
According to the passage, ionizing radiation ___.
will, in the long run, inevitably produce carcinogenicity
affects different people in different ways
is at the same time useful and dangerous
has no long term adverse effects
is the major reason for abnormalities in fetuses
We understand from the passage that no one ___.
need worry about low level exposure to radiation
can avoid diagnostic X-rays
who has not been exposed in utero to radiation has latent cancers
can escape exposure to "background" radiation
should go on with a course of radiotherapy if "early" harmful effects appear
We understand from the passage that there is considerable concern about the later appearing effects of radiation ___.
although the level of cumulative radiation that causes them is very high
since the degree of radiation needed to produce them is unknown
even though it has been demonstrated that diagnostic X-rays do not cause any such effects
particularly, as they may cause mutations in yet unborn generations
though these may include the cure for certain types of neoplasia