increased reactive oxygen species and DNA damage related to oxidative stress. In terms of the "noncarcinogenic health quotient" for components in cigarette smoke, acrolein dominates, contributing 40 times more than the next component, hydrogen cyanide. The acrolein content in cigarette smoke depends on the type of cigarette and added glycerin, making up to 220 µg acrolein per cigarette. Importantly, while the concentration of the constituents in mainstream smoke can be reduced by filters, this has no significant effect on the composition of the side-stream smoke where acrolein usually resides, and which is inhaled by passive smoking. E-cigarettes, used normally, only generate "negligible" levels of acrolein (less than 10 µg "per puff"). Chemotherapy metabolite Cyclophosphamide and ifosfamide treatment results in the production of acrolein. Acrolein produced during cyclophosphamide treatment collects in the urinary bladder and if untreated can cause hemorrhagic cystitis. Endogenous production Acrolein is a component of reuterin. Reuterin can be produced by gut microbes when glycerol is present. Microbe-produced reuterin is a potential resource of acrolein. Analytical methods The "acrolein test" is for the presence of glycerin or fats. A sample is heated with potassium bisulfate, and acrolein is released if the test is positive. When a fat is heated strongly in the presence of a dehydrating agent such as potassium bisulfate (), the glycerol portion of the molecule is dehydrated to form the unsaturated aldehyde, acrolein (CH2=CH–CHO), which has the odor peculiar to burnt cooking grease. More modern methods exist. In the US, EPA methods 603 and 624.1 are designed to measure acrolein in industrial and municipal wastewater streams. References Alkenals Hazardous air pollutants IARC Group 3 carcinogens Lachrymatory agents Pulmonary agents Foul-smelling chemicals