Diesel fumes grow new blood vessels?
New findings indicate that the link between diesel exhaust fumes and cancer lies in the ability of particles within the exhaust fumes to cause the growth of new blood vessels, which can aid tumour development.
The study investigated the impact of diesel exhaust fumes on groups of mice. The first group had an implant designed to mimic the normal conditions in the body for cell growth. In the other, the blood flow to the hind limbs was reduced, to create an area with little or no oxygen supply. During the study, the mice were exposed to either exhaust fumes or filtered outdoor air for six hours per day, five days a week. For the rest of the time, they breathed filtered air. The level of exhaust particles mimicked levels found in urban areas.
The team reported a six-fold increase in the formation of new blood vessels in the implanted tissues and aortas of mice exposed to the diesel fumes. In the mice with reduced blood supply, they saw a four-fold increase in new vessels to the hind limbs. The formation of new blood vessels is strongly associated with tumor growth; tumours grow rapidly, consuming large quantities of oxygen and nutrients.
Further tests revealed that the increased growth of new blood vessels was due to activation of biochemical pathways. In addition, in tissues exposed to the exhaust fumes there was low-grade inflammation, which is often associated with tumor development, and reduced activity of an enzyme responsible for producing tumour suppressing substances.Whilst these results indicate that diesel fumes could increase the risk of cancer development and tumour growth, the results only show that the fumes promote the growth of blood vessels. Further studies will assess the effect of exhaust particles directly on tumour development.