As the city braces for the impact of congestion pricing, concerns aren't just about the tolls but the air quality.

Environmental group 'South Bronx Unite' says diverted traffic will mean more pollution in the South Bronx. The group also says asthma hospitalizations in Mott Haven are 21 times higher than in any other neighborhoods.

The group is tracking air quality using 45 monitors across the borough, stationed in high traffic areas.

The MTA says it plans to offset pollution by removing diesel refrigeration units in Hunts Point.