The latest results on monitoring for pollution believed to be linked to the damaged Fukushima nuclear plant in Japan are expected later.
The data will be the first from testing sites across Scotland and the rest of the UK since updates changed from weekly to fortnightly reports.
The switch followed a decline in very low levels of iodine-131 detected.
The Scottish Environment Protection Agency (Sepa) and Health Protection Agency carry out the monitoring.
Sepa takes air samples from Lerwick on Shetland and from Eskdalemuir, Brydekirk, Kirtlebridge and Eastriggs, in Dumfries.
Monitoring is also done by the agency at sites in Lothian, Renfrewshire and Caithness.
The Health Protection Agency carries out air monitoring in Glasgow.
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