> 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/intro/chapter-1/1.3-water-quality-characteristics/1.3.5-radiological-screening-and-reference-values.md).

# 1.3.5 Radiological screening and reference values

Radiological safety is determined by firstly assessing gross alpha and beta activity. If both do not exceed the screening value of 0.5 Bq/L no further action is required. If either exceed 0.5 Bq/L further testing is required to determine the radium-226 and radium-228 activities. Additional radionuclides may also need to be considered. Safety is defined by not exceeding a reference value of 1.0 mSv/L per year. If the total annual dose is between 0.3 and 1.0 mSv/L further assessment and evaluation may be required.