Evaluation of carcinogenic hazard of diesel engine exhaust needs to consider revolutionary changes in diesel technology

Abstract

Diesel engines, a special type of internal combustion engine, use heat of compression, rather than electric spark, to ignite hydrocarbon fuels injected into the combustion chamber. Diesel engines have high thermal efficiency and thus, high fuel efficiency. They are widely used in commerce prompting continuous improvement in diesel engines and fuels. Concern for health effects from exposure to diesel exhaust arose in the mid-1900s and stimulated development of emissions regulations and research to improve the technology and characterize potential health hazards. This included epidemiological, controlled human exposure, laboratory animal and mechanistic studies to evaluate potential hazards of whole diesel exhaust. The International Agency for Research on Cancer (1989) classified whole diesel exhaust as - "probably carcinogenic to humans". This classification stimulated even more stringent regulations for particulate matter that required further technological developments. These included improved engine control, improved fuel injection system, enhanced exhaust cooling, use of ultra low sulfur fuel, wall-flow high-efficiency exhaust particulate filters, exhaust catalysts, and crankcase ventilation filtration. The composition of New Technology Diesel Exhaust (NTDE) is qualitatively different and the concentrations of particulate constituents are more than 90% lower than for Traditional Diesel Exhaust (TDE). We recommend that future reviews of carcinogenic hazards of diesel exhaust evaluate NTDE separately from TDE.

A rapid assessment of the impact of hazard reduction burning around Sydney, May 2016

“…For example, diesel engine exhaust (105 µg/m 3 ) appeared to be less toxic in inducing plaque development than corresponding exposures to PM 2.5 (105 µg/m 3 , 4 days/week, 5 months), indicating that some components in ambient PM 2.5 , which are not present in diesel engine exhaust, are responsible for exacerbating plaque progression (Quan et al, 2010). In their recent review, McClellan, Hesterberg & Wall (2012) pointed out that, although there are good reasons for concern for health effects due to diesel engine exhaust exposure, significant efforts have been made to abate the composition of diesel engine exhaust in the past few decades, resulting in a more fuel efficient and complete combustion process and the installation of filter traps with substantial lower mass emissions. It seems very likely that this will have a profound effect on the toxicity of diesel engine exhaust, but there is no systematic review available that allows clear conclusions on an increase or decrease of the toxic potency and associated health risks.…”

Combustion and emissions characteristics of a dual fuel engine operated on alternative gaseous fuels

“…That exhaust is of concern because of its impact on visibility and for its potential health hazards. Particulate emissions can be classified as potential occupational carcinogen and can have a number of other negative health impacts associated with exposure [3][4][5][6]. It is generally agreed that diesel engines used in transport systems represent an important source of ambient particulate matter [7].…”

Microbial Growth Control in Diesel by Optimization of Sulphur

“…The low volatility of diesel provides larger time and areas of contact between the microbe and the fuel. Diesel engines have high thermal capacity and high fuel efficiency (McClellan et al, 2012). A variety of additives may be used to improve the stability of the fuel; these include compounds such as aliphatic amines, chelating agents, detergents and corrosion inhibitors, some of which can act as a nutrient source for microorganisms.…”