Table 1 Examples of endogenous and exogenous factors that result in oxidant formation
EndogenousExogenous
Electron transport chains (mitochondria, endoplasmic reticulum, plasma membrane)Radiation (high energy, UV, visible light + sensitizer, thermal, ultrasound)
Haem protein/enzyme reactions (e.g. haemoglobin, myoglobin, cytochromes such as cytochrome P450)Metabolism of chlorinated hydrocarbons, drugs, nitro compounds, paracetamol, ethanol
PeroxidasesNitrogen oxides (NOx)
Nitric oxide synthases (NOS)Particulates (e.g. diesel particles)
NADPH oxidases (NOx)Mineral fibres and dusts (e.g. asbestos)
Xanthine oxidaseOzone
LipoxygenasesSulfur oxides (SOx)
Prostaglandin synthasesOxidized foodstuffs
Autooxidation of glucose, thiols, catecholamines, metal ionsCombustion processes (e.g. smoking)Metal ion overload (e.g. Fe, Cu)