<html><head></head><body lang="en-GB" style="background-color: rgb(255, 255, 255); line-height: initial;"> <div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);">Dear Dean</div><div style="width: 100%; font-size: initial; font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; color: rgb(31, 73, 125); text-align: initial; background-color: rgb(255, 255, 255);"><br></div><div>"The government is trying to switch to natural gas especially because <span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;">coal burning produces carcinogens."</span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><br></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;">I have read this claim about carcinogens a number of times and I am wondering if you have seen much to back it up. I have read fuel analyses for years and the claim of 'carcinogens' seems to be more 'what to say when you want to bash coal' than something supported by the analysis of the fuel. </span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><br></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;">If one were to say 'combustion of coal produces carcinogens' another can say it is the <i>failure</i> to burn the coal that leads to 'carcinogens'. The same is true for wood. A bad wood fire can produce lots of carcinogens, none of which are in the fuel if one analyses it, which means the problem is not the fuel. </span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><br></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;">Kirk Smith makes much of the coals in western and/or is it south Western China that have fluoride in them. All the water in the area will have fluoride as well, something well documented so it is hardly news, and bad as it is for bones and health, I don't think fluoride is technically a 'carcinogen'. Maybe Frans can comment. </span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><br></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;">The reason I ask is the claim in the introduction of the Stove Comparison Chart mentions that some coal (at least in one region of China) has fluoride in it and concludes, if you can call it a conclusion, that people therefore shouldn't burn coal. At all...because in China some of the coal on one area has picked up fluoride from the water table. That doesn't seem like a very good reason to ban all the coals in the world. </span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><br></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;">Coal is old biomass and there is no general claim that it is all the same. So when you rattle off "coal has carcinogens" I always wonder where they are. Well-burned coal combustion emits CO2, CO, water vapour and depending on the mineralisation, a small amount of trace minerals which vary widely composition. </span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><br></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;">Tobacco is only carcinogenic if it is <i>not</i><span> burned well. It is the same with teak or palm kernels. </span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span><br></span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span>It is often claimed that 'coking' or 'semi-coking' coal 'removes pollution' and 'makes it a clean fuel'. This is just nonsense. What is 'removed' is just CHO in one form or another that some combustors don't burn well. Too bad for the designer. But it is not right to misrepresent what is removed as 'carcinogens' any more than saying it is 'smoke' or 'pollution'. It is just carbonaceous volatiles. The stove designing community has to get ahead of this curve. Perfectly burned wood or coal or LPG or ethanol or dimethyl ethylene emits the same combustion products. </span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span><br></span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span>What is universally bad news is bad combustion. Coal burned badly has terrible consequences. So what? Why then not burn it properly? Why blame coal for the faults of the designer, manufacturer or operator? All carcinogens are the responsibility of the designer save in occasional cases related to local contamination. Is this true or not? I don't want the misrepresentation to fall in either direction. </span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span><br></span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span>If we are going to generalise, I think there has to be some general proof and it is going to have to be pretty convincing. </span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span><br></span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span>Thanks to anyone who can assist with this topic. It is time we addressed it because hundreds of millions of people rely of fuels that are being characterised as 'dirty' instead of the stoves that don't burn them properly. </span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span><br></span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span>Regards</span></span></div><div><span style="line-height: initial; color: rgb(31, 73, 125); font-family: Calibri, 'Slate Pro', sans-serif, sans-serif; font-size: initial; text-align: initial;"><span>Crispin </span></span></div><br></body></html>