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What happens when things burn?

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What happens when things burn?. in a “perfect world” combustion reduces everything to carbon dioxide and water vapour (complete combustion) hydrocarbon + air (oxygen) → CO 2 + H 2 O heat … unfortunately, we don’t live an a perfect world …. What happens when things burn?.

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What happens when things burn?
  • in a “perfect world” combustion reduces everything to carbon dioxide and water vapour (complete combustion)
  • hydrocarbon + air (oxygen)→CO2 + H2O
  • heat
  • … unfortunately, we don’t live an a perfect world …
What happens when things burn?
  • in the “real world” combustion is incomplete, which means we get many other products of combustion
  • hydrocarbon + air (oxygen)→CO2 + H2O
  • heat
  • + CO + NOx + SOx + benzene + HCN + PAH’s + dioxins + heavy metals + ?
What happens when things burn?
  • the conditions of combustion also have an influence on the products of combustion
  • temperature – hotter fires usually burn the fuel more completely
  • ventilation (oxygen availability) – lack of oxygen will encourage chemicals to reconfigure
  • fuel – chemical composition of what is burning will determine products of combustion
What happens when PVC burns?
  • polyvinyl chloride contains significant quantities of chlorine ( up to >50%) and so one of the main products of combustion is hydrochloric acid (HCl)
  • PVC + air (oxygen)→CO2 + H2O + HCl
  • heat
  • + CO + NOx + SOx + benzene + HCN + PAH’s + dioxins + heavy metals + ?
What happens when PVC burns?
  • solid polyvinyl chloride (PVC) plastic first melts with increasing temperature, then at a certain point the polymer structure starts to unzip. next the chlorine and hydrogen start to be released (forming HCl)
  • as the hydrocarbon base starts to loose hydrogen, the carbon begins to form more concentrated carbon molecules (aromatic hydrocarbons such as benzene)
What happens when PVC burns?
  • if there is sufficient oxygen around the carbon oxidizes and forms carbon dioxide (CO2) and some carbon monoxide (CO)
  • the air that gets involved with combustion beside supplying oxygen also has nitrogen (78%), at high temperatures nitrogen compounds begin to form (nitrogen oxides (NOx) and hydrogen cyanide (HCN)).
What happens when PVC burns?
  • soot formation happens when there is insufficient oxygen for ideal combustion and so the carbon concentrates into joined aromatic rings (polycyclic aromatic hydrocarbons PAH’s) and ultimately into elemental carbon (carbon with no hydrogen or oxygen)
  • the presence of chlorine complicates matters and with some oxygen present, dioxins & furans will form
What was measured at the fire?
  • the MOEE had a mobile unit on site to measure community air quality (not firefighter breathing zone air quality)
  • the closest they got to the fire was 100 m but usually further away
  • when the fire was burning vigorously the plume went up and over the mobile unit
  • the fire dept used MOEE data to locate rest areas
What was measured in the plume?
  • MOEE measurements were taken behind the firefighters working and resting positions
  • Dr. Brian McCarry (McMaster) took measurements on the roof of a neighbouring building, often in the plume
  • the difference was 50-700 fold more exposure in the plume
what are the health implications of such exposures
What are the health implications of such exposures?
  • Colin has already described the initial symptoms he and his co-workers experienced
  • with the media reports of the presence of dioxin in the air and runoff – workers were very concerned about future health effects particularly cancer
getting workplace cancers recognized as such
Getting workplace cancers recognized as such:
  • Colin and the IAFF have worked tirelessly to get the WSIB to recognize that the 5 cancers were related to firefighter exposures
  • if the link between exposures and cancers are not recognized, prevention efforts are hampered
how much cancer is recognized as work related
How much cancer is recognized as work-related?
  • Siemiatycki (1995) produced estimates of the population attributable risk due to occupational exposure for 9 cancers using 3 different approaches (e.g. the attributable portion of lung cancer ranged from 8-20%)
  • Siemiatycki’s group interviews people in the Montreal area with cancer to get an exposure history for each cancer patient seen at the cancer clinics

estimate of ontario burden of occupational lung cancer
Estimate of Ontario burden of occupational lung cancer:
  • actual new cases of lung cancer in Ontario in2001 were 3900 males and 3100 females
  • using Siemiatycki’s range of estimates of the burden of occupational lung cancer (8-20%) the number of occupational lung cancers would be between 560-1400 cases
  • In 2001 the WSIB recognized only 7 cases (0.1%) of cancer (all types except mesothelioma)
why aren t occupational cancers recognized
Why Aren\'t Occupational Cancers Recognized?
  • cancer is poorly understood
  • multi-factorial causes
  • latency
  • default assumption is not work-related given an absence of evidence
  • occupational health not well understood in medical field
  • although exposure has declined, the rates of asbestos-related diseases are still climbing
Not all cancers are the same …
  • Ontario research has shown that for some cancers, more recent exposures are more closely associated with the cancer development than older exposures
  • for benzene caused leukemia, exposures in the last 5-15 years had a stronger association with the development of leukemia than exposures 20 or more years before
Not all exposures are the same …
  • a fundamental rule in toxicology is called Haber’s Rule, which states that the dose multiplied by the time over which it is delivered is equal to a constant:
  • C x T = k (C=concentration, T=time)
  • however, research with benzene has shown that peak exposures leave more damage than the equivalent dose spread over a longer exposure time (in contradiction of Haber’s Rule)
Firefighter exposures & diseases:
  • firefighter exposures are relatively brief and intense – unlike other occupations where workers experience similar exposures each day
  • firefighters have also had higher rates of the occupational cancers with lower latency times
  • firefighters also have similar exposures to “cancer promoters” – substances which in themselves don’t initiate cancer, but provide the conditions in tissues where existing tumours develop faster
What does this mean for the general population/environment?
  • firefighter are the “canaries” for society
  • as we rely more and more on plastics and high technology, firefighters are the first ones there during catastrophic events involving these materials
  • firefighter health serves as a sentinel indicator of population health

… any questions, comments …