What happens when things burn?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?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?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?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 + HClHCl heat

+ CO + NOx + SOx + benzene + HCN + PAH’s + dioxins + heavy metals + ?

What happens when PVC burns?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?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?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?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 at the fire?What was measured at the fire?exposure concentration env std

benzene 0.26 ppm 0.0001 ppmhydrogen chloride 0.62 ppm 0.067 ppmPAH’s (as B[α]P) 0.5-1.0 ng/m3 1.5 ng/m3

dioxins/furans (as TEQ) 2.8-19.3 pg/m3 5.0 pg/m3

lead 10.1 μg/m3 2.0 μg/m3

chromium 5.7 μg/m3 1.5 μg/m3

nickel 6.4 μg/m3 2.0 μg/m3

What was measured in the What was measured in the plumeplume??

exposure McMaster MOEEPAH’s (as B[α]P) 354 ng/m3 0.5-1.0 ng/m3

dioxins/furans (as TEQ) 1012 pg/m3 2.8-19.3 pg/m3

• 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 What are the health implications of such exposures?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 Getting workplace cancers recognized as such: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 How much cancer is recognized as work-related?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

http://ehp.niehs.nih.gov/members/1995/Suppl-8/siem-full.html

Estimate of Ontario burden of Estimate of Ontario burden of occupational lung cancer:occupational lung cancer:

• actual new cases of lung cancer in Ontario in 2001 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)

How many lung cancers in Ontario How many lung cancers in Ontario are recognized as occupational?are recognized as occupational?

22 7

560

1400

0200400600800

100012001400

# of WSIB claims

accepted

2001year

WSIB recognized mesotheliomas WSIB recognized all other cancersoccupational lung cancers (lo est.) occupational lung cancers (hi est.)

Why Aren't Occupational Why Aren't Occupational Cancers Recognized?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

LatencyLatency• although

exposure has declined, the rates of asbestos-related diseases are still climbing

Not all cancers are the same …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 …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 & 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 What does this mean for the general population/environment?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

thank–you

… any questions, comments …