The Center’s literature citation database located on this web site was updated in the summer of 2001 by adding 640 new citations on the exposure atmospheres (source emissions) and health responses under study by the Center.  The searchable, publicly-accessible database now contains well over 22,000 citations.

Exposures to hardwood smoke, the second complex atmosphere, began on June 3, 2002, and have proceeded without incident.  Smoke is generated by burning oak at 19–25% moisture in a non-certified conventional wood stove using a three-phase daily burn cycle: 1) kindling with blank newsprint; 2) high burn with open damper; and 3) low burn with nearly closed damper.  Although concentrations vary over the course of the daily cycle, the target mean daily concentrations have been met with less difficulty than expected.  Dilutions are set to achieve respirable particle levels identical to those used in the diesel study (1000, 300, 100, and 30 µg/m³).  The exposures will continue through January 2003 to accommodate the various exposure patterns and health measurements in the protocol.  Opportunities exist for collaborative use of both the exposure atmosphere and biological samples not required by the NERC study protocol.

A workshop of LRRI staff and technical experts from EPA, DOE, and the automotive and petroleum industries was held in February 2002 to develop recommendations for generating the third exposure atmosphere, “on-road gasoline engine emissions.”  The group reached consensus on recommending the following: 1) a mid-mileage (40,000–60,000 miles) 1996 model medium-sized light-duty engine (4.0–4.3 liter) from Chrysler, General Motors, or Ford; 2) the Unified Driving Cycle (UDC), a variable-duty urban cycle; and 3) a fuel blended to represent a “national average” containing 300 ppm sulfur and no oxygenates.  This strategy was approved by the Center's External Scientific Advisory Committee at its May 2002 meeting, and the processes of obtaining the engines, resolving fuel and safety issues, and “mapping” the UDC from its typical use with vehicles on a chassis dynamometer for use with engines on test stands has begun.

Three mid-mileage Chevrolet S-10 pickups with 4.3 liter engines, automatic transmissions, and normal emissions will be “recruited”; the engines and associated engine and emissions controls will be removed, two engines will be mounted on test stands in the exposure laboratory to enable two “cold starts” per day, and the third will be on reserve as a spare.  The exhaust dilutions (exposure concentrations) have not yet been set, but it is clear that the particle concentrations will not be identical to those used for the diesel and wood smoke studies.  The exposures will not begin until the spring or summer of 2003.

Discussions have begun in preparation for holding a workshop to develop recommendations for the fourth exposure atmosphere, “coal combustion emissions.”  Specifying and conducting this exposure promises to be more challenging than the first three.  Although people are exposed to fresh emissions from engines and wood stoves (albeit also exposed to aged emissions), people are not exposed “at the top of the stack” of a coal-fired utility boiler.  From the beginning, it was envisioned that the coal atmosphere would contain components, such as sulfate particles, that are formed downstream from the point of emission, in addition to those components emitted at the stack.  It is anticipated that the workshop will be held in January 2003 and that the exposure to the “coal combustion” atmosphere will be conducted during 2004.