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 at the fire?
exposure
benzene
hydrogen chloride
PAH’s (as B[α]P)
dioxins/furans (as TEQ)
lead
chromium
nickel
concentration
env std
0.26 ppm
0.0001 ppm
0.62 ppm
0.067 ppm
0.5-1.0 ng/m3
1.5 ng/m3
2.8-19.3 pg/m3 5.0 pg/m3
10.1 μg/m3
2.0 μg/m3
5.7 μg/m3
1.5 μg/m3
6.4 μg/m3
2.0 μg/m3
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
exposure
PAH’s (as B[α]P)
dioxins/furans (as TEQ)
McMaster
MOEE
354 ng/m3 0.5-1.0 ng/m3
1012 pg/m3 2.8-19.3 pg/m3
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:
• 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?
• 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
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 5601400 cases
• In 2001 the WSIB recognized only 7 cases (0.1%) of
cancer (all types except mesothelioma)
How many lung cancers in Ontario
are recognized as occupational?
1400
1400
1200
1000
# of WSIB 800
claims
600
accepted
560
400
200
0
22
7
2001
year
WSIB recognized mesotheliomas
occupational lung cancers (lo est.)
WSIB recognized all other cancers
occupational lung cancers (hi est.)
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
Latency
• although
exposure has
declined, the
rates of asbestosrelated 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 515 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
thank–you
… any questions, comments …