The actual trends in finding better surrogates (more specific) are listed in this slide. A few European countries (Germany, Switzerland) have chosen the Ť elemental carbon ť as the most appropriate surrogate since it represents the core of the diesel exhaust particulate and is more specific than the total carbon index. However, the measurement of this parameter is Ť method dependent ť and is not quite specific either.

It becomes more and more obvious that the mass of the particulates may not be the most relevant index of exposure since the health effects are probably more linked to surface properties of the particles or to their number than to their weight.