> For the complete documentation index, see [llms.txt](https://guidelines.nhmrc.gov.au/australian-drinking-water-guidelines/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://guidelines.nhmrc.gov.au/australian-drinking-water-guidelines/part-2/chapter-7/7.1-introduction.md).

# 7.1 Introduction

This chapter describes the sources of radiation in the environment and in drinking water, the health effects of radiation, how people are exposed to radiation and how radiation exposure is measured. It also explains how the reference levels and screening values provided in Chapter 10 are derived.