The particles found are up to 10 times higher than on the streets outside and up to eight times above the World Health Organisation's recommended daily limit.
According to experts passengers on the subway for 45 minutes are exposed to potentially breathing in 60 million particles. The partials which are mostly made up of iron oxide from the grinding of the railway track. The particles are thought to be less dangerous than those found from diesel cars and trains although campaigners are encouraging this to be further investigated.
The results where measured on a 40 minute journey May 10th 2013. A portable, state-of-the-art monitor detected concentrations of between 40 million and 80 million particles per cubic metre of air.
Dr Richard Dixon, the director of Friends of the Earth Scotland said "This problem urgently needs further investigation. Confirmation of these results would require decisive action to reduce pollution"
However, SPT described the Sunday Herald survey as sensational and alarmist. It complained it had not been shown the full scientific evidence, or details of how the survey was conducted.
"There are a huge array of factors during even the shortest journey which can impact on pollution monitors, and it is not clear from this snapshot if that has been taken into consideration," said an SPT spokeswoman.
"However, SPT takes both passenger and staff health very seriously and uses respected industry expertise to guide us on best practice in the subway."
Source: Herald Scotland