In most cases, the radiation hazard is much greater than the chemical (toxic) hazard. Radiation protection limits are lower than the chemical hazard protection limits would be. By issuing radiation protection regulations, EPA can protect people from both the radiation and the chemical hazard. However, deciding which hazard is greater is not always straightforward. Several factors can tip the balance:

toxicity of the radionuclide
strength of the ionizing radiation
how quickly the radionuclide emits radiation (half-life)
relative abundance of the radioactive and non-radioactive forms

For example

Uranium-238 radioactive and very toxic. Its half-life of 4.5 billion years means that only a few atoms emit radiation at a time. A sample containing enough atoms to pose a radiation hazard contains enough atoms to pose a chemical hazard. As a result, EPA regulates uranium-238 as both a chemical and a radiation hazard.

Radioactive isotopes of lead are both radioactive and toxic. In spite of the severe effects of lead on the brain and the nervous system, the radiation hazard is greater. However, the radioactive forms of lead are so uncommon that paint or other lead containing products do not contain enough radioactive lead to present a radiation hazard. As a result, EPA regulates lead as a chemical hazard.

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