Scott A. Fruin, Arthur M. Winer and Charles E. Rodes: Black carbon concentrations in California vehicles and estimation of in-vehicle diesel exhaust particulate matter exposures. Atmospheric Environment, Volume 38, Issue 25 , August 2004, Pages 4123-4133

J. Gulliver and D. J. Briggs. Personal exposure to particulate air pollution in transport microenvironments. Atmospheric Environment, Volume 38, Issue 1 , January 2004, Pages 1-8

A. K. Mukherjee, S. K. Bhattacharya, S. Ahmed, S. K. Roy, A. Roychowdhury and S. Sen. Exposure of drivers and conductors to noise, heat, dust and volatile organic compounds in the state transport special buses of Kolkata city. Transportation Research Part D: Transport and Environment, Volume 8, Issue 1 , January 2003, Pages 11-19

Other sources

The TERI website has a bibliography of in-vehicle exposure studies:
http://www.teriin.org/indoor/biblio.htm#exposure

The Hong Kong Polytechnic University has similar studies that can be downloaded:
http://www.cse.polyu.edu.hk/~activi/Paper/