Probably do, but gassers produce particulate matter (PM) too...is that a concern? Do you know of any studies that exhonerate gassers' cancer concerns?

First of all, both of my vehicles are diesels (one of which is a TDI), so I'll admit to a bias here. However, I have to challenge some of what I consider misconceptions about diesel emissions (I've been an environmental professional for over 20 years).


Point: Diesel emissions cause cancer.

Counterpoint: Assays of gasoline and diesel PM and semi-volatile organic compounds demonstrate that gasoline emissions show a positive response in 5 of 6 categories of mutagenicity, DNA damage, chromasomal damage. Diesel emissions showed a positive response in 2 of 6 categories.

Source: In Vitro Genotoxicity of Gasoline and Diesel Engine Vehicle Exhaust Particulate and Semi-Volatile Organic Compound Materials

Presented at the 2002 DEER Conference


For cytotoxicity, high emitting gasoline engines demonstrated a much higher response than even old, high emitting diesel engines. (That's why I try to avoid following old/poorly maintained GASSERS on the road!) "Normal" emitting gas and diesel engines exhibited essentially the same cytotoxicity.

Source:

COMPARATIVE TOXICITY OF COMBINED PARTICLE AND SEMI-VOLATILE ORGANIC FRACTIONS OF GASOLINE AND DIESEL EMISSIONS

Presented at the 2002 DEER Conference


Gasoline engines emit approximately ONE ORDER OF MAGNITUDE more benzene (a known carcinogen) than a comparable diesel engine (and this doesn't even take into account fugitive benzene emissions from gasoline fuel transfer).

Gasoline engines emit numerically more PM and more polycyclic aromatic compounds (many of which are considered carcinogenic) than equivalent diesels under many real-world driving conditions.

Most harmful gaseous emissions were lower for diesel.

Source:

Environmental and Health Impact From Modern Cars
May 2002


Point: Diesels cause "smog".

Counterpoint: The ozone forming potential was considerably lower for diesel cars, i.e., roughly one order of magnitude lower than for petrol cars. This is mainly due to the low level of HC emissions for diesel cars compared to petrol cars. Should the evaporative emissions have been taken into account, the relative differences would have been even greater.

Source:

Environmental and Health Impact From Modern Cars
May 2002

Gasoline exhaust and gasoline vapor account for ~80 percent of ambient NMHC in on-road samples and at regional air monitoring locations suggesting that gasoline emissions are responsible for the majority of ozone found in the SoCAB.

Source:

DOE’s Studies of Weekday/Weekend Ozone Pollution in Southern California

Presented at 2002 DEER Conference


Point: Fuel Cells are the most efficient energy converters known.

Counterpoint:

...the ranking between drive systems is (with one exception) the same independent of motor fuel type, namely:

-hybrid with diesel-engine
-hybrid with fuel cell
-direct operation with fuel cell
-hybrid with otto-engine
-conventional diesel-engine
-(hybrid with direct-methanol fuel cell)
-conventional otto-engine.

(This is taking the energy required for fuel production into account.)

Source:

Well-to-Wheel Efficiency For Alternative Fuels From Natural Gas or Biomass

October 2001


Which brings up one more point (or counterpoint): why are hybrids only mentioned with gas engines, as if diesels with hybrid drive trains are mutually exclusive? If a VW Lupo with a 1.2 liter TDI and a more or less conventional transmission can achieve nearly 100 mpg (U.S.) in its "around the world in 80 days" tour, I contend that a diesel hybrid Civic would get significantly better fuel mileage than an equivalent gasoline-hybrid Civic!