High levels of radon gas can pose a major risk to the health of hundreds of families residing in Scotland.
More than 2,000 testing kits were sent out in Aberdeenshire and the Highlands in 2011 and 800 homes were found to have higher-than-normal levels of radon, the BBC reported.
Radon is a natural radioactive gas, which comes from small amounts of uranium found in rock and soil.
Although the levels are generally low, it is believed to cause more than 1,000 deaths across Britain each year.
According to an indicative map published in July last year, concentrated pockets were found particularly along Deeside in the north east.
"We fully understand that when some people received their radon results they may have been surprised or even a little concerned because having a letter drop through the door telling you that your family is exposed to radiation could be unsettling for some people," said Neil McColl, of the Health Protection Agency's centre for radiation, chemical and environmental hazards.
"Sadly, ignoring radon isn't a safe option. Failing to deal with high radon levels just increases your exposure and the risk to the health of you and your family. We are here to help and want to say to those who, for whatever reason, missed us when we ran local events that we're only a phone call or an email away," said McColl
The agency said that Radon produces a radioactive dust in the air.
The dust is then trapped in airways and emits radiation that causes damages to the inside of lungs.
"We are encouraging everyone who has received high radon results to come forward and find out more about radon and what they can do to their homes to lower levels," said Public Health Minister Michael Matheson.
"Radon cannot be detected by sight or smell but we now know that hundreds of homes across the north of Scotland have higher-than-safe levels. Failing to deal with high radon levels increases your exposure to it and in the long term this can be a health risk," he added.