Government would only spray killed bacteria - and only in off hours - in Red Line bioterror attack tests

The Department of Homeland Security says the moves will ensure the tests, planned for this summer at Harvard, Porter and Davis on the Red Line, pose no risk to riders with immune problems, according to a DHS report - unlike fellow riders or snakes.

The release of B. subtilis spores will mimic a possible bioterror attack and test the efficiency of scanners to provide early warnings of possible biologic attacks - in as little as 20 minutes after the release of bacteria.

B. subtilis is generally considered harmless - you can even buy it as a "probiotic" nutritional supplement - but the environmental assessment, prepared for the DHS Science and Technology Directorate, rules out the idea of using live bacteria released during normal commuter hours:

While the probability that an infection of a vulnerable subway rider may occur is very low due to the small number of spores proposed to be released in the station during testing, the consequences of any infection caused by the proposed testing are not acceptable and, as such, the use of viable spores in open air challenge testing of the biosensor system is not recommended.

Instead, the department will use spore samples irradiated with gamma rays and released overnight. The dead spores can still be detected by scanners, but cannot infect anybody, DHS says. The T will run trains during the testing period because air movement caused by trains is a major way bioweapons would be dispersed in a subway.

DHS approached the MBTA for its testing because it's a large system in a regions with temperature extremes and because of earlier testing on the T that involved the release of dyes and gases.

Within the MBTA system, the three adjacent stations of Porter, Davis, and Harvard were selected as test locations due to previous airflow modeling efforts that could be leveraged for this test, as well as the ease of sensor installation in these locations.

DHS holds a public hearing on the proposed testing at 5:30 p.m. on May 16 at the YMCA in Central Square, Cambridge. Comments can be submitted to [email protected].