Outdoor Air Quality: Smoke and Air Pollution at Work with Dr. Denise Koh

submitted for publication Safe Work Matters December, 2018

Climate Change Impact on AQ: 

Due to Manitoba’s northern latitude and continental geography, our province is projected to continue to see rapid changes in our climate--warming much faster than the global average--with significant major disruptions in our social, economic, and ecological systems, industry sectors, and health.  Climate Change and higher temperatures will increase smog pollution as well as wildfires, due to the drying of the forest floor with elevated heat and drought.  This year Manitoba had 472 wildland fires which burnt 218,000 hectares.  Canada’s wildfires prompted air quality advisories by Environment Canada.

The Canadian Medical Association estimated that the Illness Cost of Air Pollution (ICAP) in 2008 was $8 billion in Canada for lost productivity, healthcare costs, quality of life, and loss of life.  Approximately 21,000 deaths could be attributed to air pollution, together with 11,000 hospital admissions and 92,000 emergency department visits (http://www.cma.ca/index.cfm/ci_id/86830/la_id/1.htm).

Composition: 

Air pollution and smoke contain a complex mixture of gases and particulate matter formed during natural (forest fires, volcanoes, dust storms) and human-made processes (transport, power generation, industrial activity, heating, cooking, and fuel or coal combustion).   Particulate matter is a complex mixture of solid particles and liquid droplets suspended in air and is categorized according to size:  Total suspended particulates (TSP; particles less than 40 µm in diameter), Coarse PM (2.5–10 microns), Fine PM (< 2.5 um), and Ultrafine PM (<1um).  Ultrafine particles are formed directly in combustion exhaust, mainly as hot vapours are condensed, and can aggregate and coagulate over time to form fine particulates.  In contrast, particles in the fine fraction are produced mainly by combustion processes and by atmospheric reactions between precursor gases such as sulfur dioxide, nitrogen oxides, ammonia, and some volatile organic compounds.

The composition of outdoor air pollutants may vary over time and space (due to variations in the pollutants’ sources, changes in weather and atmospheric transformations) and is difficult to characterize and measure.  Major gaseous pollutants include sulfur dioxide, nitrogen oxides, and carbon monoxide. Major particulate matter components include organic and elemental carbon compounds, metal oxides, lead, and others.

Wildland fire smoke composition depends on unpredictable/uncontrollable factors such as the source of the fire, moisture content, topography, and meteorological conditions.  The fire emission plume comprises a mixture of 100s of toxic by-products including asphyxiants (CO, hydrogen cyanide, and CO₂₎, irritants (sulfur dioxide, nitrogen oxides, phosphorus pentoxide, HCl, HF, HBr, acrolein and aldehydes), complex organic contaminants (polycyclic aromatic hydrocarbons, dioxins and dibenzofurans/benzene) and particulate matter (may contain adsorbed metals & organic contaminants).   While measuring exposure is logistically challenging, studies have generally found that the average exposures to specific toxins are lower than established Occupational Exposure Limits, but, on occasion, they may be elevated.

Air Quality Health Index:

The AQHI is an indicator which can be useful for present and forecasted air quality.  It reflects the concentrations of 3 major components of air pollution which are important predictors of the impact of the mix of air pollutants on mortality:  nitrogen dioxide (comes out of vehicle tailpipes, increases during rush hour), ozone (formed by a complex chemical reaction from other pollutants; requires sunlight & heat to form), and PM_2.5 (particles <=2.5 micrometers in diameter). The resulting ratings range from 1 to 10+ and are grouped into risk categories designed to help users easily and quickly identify their level of risk.  Each category has specific health advice for those at risk (children, seniors, people with heart or lung conditions and diabetics) and the general population.

Health Effects:

The health effects of air pollution and smoke depend on:

·         The length of time we are exposed

·         How much air we breathe in

·         Our health status

·         The concentration of smoke/pollutants in the air.

Particles that are 10 micrometers in diameter or smaller pose the greatest problems.  Larger particles (>10 um) usually do not enter the lungs, although they can still irritate the eyes, nose, and throat.  The smaller particles enter the lungs, making it harder to breathe or triggering cough.  They can affect the lungs and heart, where they can cause serious health effects or make existing conditions worse. 

Both short-term and long-term particle pollution exposures have been linked with health problems. 

Short-term Air Pollution Health Effects:

• ·        Exacerbation of pre-existing lung disease: increased symptoms such as coughing, wheezing, and shortness of breath.

o   Asthma: the median proportion of adult cases of asthma attributable to occupational exposure is 10% - 15%.

o   Chronic Obstructive Pulmonary Disease:  includes chronic bronchitis and emphysema

• ·         Exacerbation of pre-existing cardiovascular disease: Particulate matter affects heart rate variability, blood pressure, vascular tone, blood coagulability, and the progression of atherosclerosis.

o   Ischemic Heart Disease

o   Heart failure

o   Arrhythmias and cardiac arrest:  PM was associated with increased odds of atrial fibrillation onset within hours following exposure in patients with known cardiac disease.  Even low levels of air pollution causes AF.

§  For an increase of 10 μg/m³ in PM_2.5, there was a 4%–10% increase in the number of arrests out-of-hospital. The likelihood of being resuscitated from an out-of-hospital cardiac arrest in large metropolitan areas is among the lowest, with survival ranging from about 1%-3%

o   Ischemic stroke and TIA (mini stroke)

o   Peripheral Vascular Disease

• ·         Increased Hospitalization/ Emergency Department visits

     Long-term Air Pollution Health Effects:

• ·         Increased mortality: can reduce life expectancy by a few years.
• ·         Increased incidence of Ca lung, stomach; pneumonia

o   IARC Group I, carcinogenic to humans:  focused on pollutants released as a result of human activities, especially combustion and industrial processes.

o   Sufficient evidence of an association bw exposure and lung cancer; limited evidence that exposure causes bladder cancer.

o   Sufficient evidence supporting the carcinogenicity of various components of outdoor air pollutants in animal studies.

§  Whole diesel engine exhaust, diesel engine exhaust particles, extracts of diesel engine exhaust particles, condensates of gasoline engine exhaust, extracts from coal-derived soot & wood smoke, & emissions from combustion of coal & wood

o   Strong evidence that outdoor air pollution has genotoxic effects.

• ·         New onset of asthma (Stieb, 2015; McConnell, 2010; Dell, 2008)
• ·         Reduced lung development in children (Gauderman NEJM 2004)
• ·         Development of atherosclerosis (Brooks RD Curr Atheroscler Rep 2010)

o   A Greek 2014 study found that the impact on CVD and IHD illness from long-term exposure to traffic-related air pollution was particularly strong among women and younger subjects.

o   Studies showed an increased risk of ischemic heart disease in workers exposed to air pollution (police workers, professional drivers, mail carriers, filling station attendants, road cleaners, garage workers, motor vehicles and engine maintenance).  The link was stronger between motor exhaust and particulate matter and IHD. 

o   A study on traffic police officers found that one hour on duty outdoor per day for one year led to an increase in certain markers in the blood; the researchers concluded that air pollution may lead to metabolism adaptation and it is likely involved in the development of CVD and DM (Tan, 2018)

o   Traffic officers also experienced exercise-induced ECG abnormalities, high blood pressure and changes in oxygen saturation of the blood.  It was concluded that air pollution reduces resistance to physical effort and increases the risk of cardiovascular and respiratory changes.

• ·         Associated with increased incidence of DVT, stroke
• ·         Pregnancy effects:  assoc with pre-term birth and low birth weight
• ·         Exposure to air pollution affects hormone levels:

o   Luteinizing hormone in female traffic police 

o   Low concentrations of Cd in urban air affects thyroid hormone levels in exposed workers

•      In Mexico City, outdoor workers had greater DNA damage and a greater percentage of highly damaged cells than indoor workers; DNA damage magnitude was positively correlated with PM_2.5 and ozone exposure.

o   Highly damaged workers (> or =60% of highly damaged cells) had significantly higher exposures to PM_2.5, ozone, and some volatile organic compounds.

• ·         Ambient air pollution may impact human olfactory function.

Wildland Fire Fighters:

These workers often face long work shifts, repeated daily for many consecutive days or weeks. Exhaustion, dehydration, poor diet, and lack of sleep are possible consequences of this demanding work schedule.  They are exposed to a complex mixture of organic material thermal breakdown and decomposition.  Outdoor exposure levels can be mitigated by winds and convective currents, and workers may have the freedom to position themselves in less polluted areas or work upwind.  For pragmatic reasons, these workers rarely wear respirators.  Some rely on bandannas, which may be psychologically reassuring and act as a minor heat barrier, but in reality a bandanna offers no protection against hazardous airborne toxins.

One study found a decline in lung function following a full season of firefighting compared to preseason values.  While there was an eventual return to baseline during the post season, the recovery period was still months after exposure.  Since no significant change in lung function was found pre- and post-shift, it was concluded that lung function decline is not an acute event but rather associated with longer smoke exposures.  However, the cumulative effect of repeated wildfire smoke injury and repair cycles on the lung is completely unknown.

Change in levels of urine and blood markers of these workers suggest that local lung inflammation and oxidative stress are important outcomes of wildfire smoke exposure.  Oxidative stress serves as an indicator of arterial stiffness for firefighters, who have a higher oxidative stress score after encountering a fire.

AP and Productivity:

Studies have shown that outdoor ozone and air pollution reduces the output of farm and factory workers.   Even ozone levels well below air quality standards can have a significant impact.  A 10 parts per billion decrease in ozone concentration in outdoor air increases worker productivity by 4.2 %. 

Researchers in China studied the effect of air pollution on call-center workers and found a 10-unit increase in air quality index led to a 0.35% decline in # calls handled.  Workers were 5%–6% more productive with good air quality index levels vs unhealthy levels.  Productivity was again affected when AQI levels were relatively low (at the level common in major North American metropolitan areas). Air pollution can cause inflammation of the central nervous system, cortical stress, and cerebrovascular damage.  Greater exposure to fine PM is associated with lower intelligence and diminished performance over a range of cognitive domains.

At Risk Workers:

•          Workers in any number of jobs may be exposed
•          Outdoor workers in close proximity to the source
•          Those performing strenuous activities are most exposed because they are breathing air deeply and rapidly
•          Those workers whose health is compromised (sensitive worker populations) 
• Workers with existing respiratory conditions—such as asthma, lung cancer, chronic obstructive lung disease (COPD) including chronic bronchitis and emphysema
• Workers who smoke with compromised lung function
• Workers with existing cardiovascular conditions including:  angina, previous heart attack, congestive heart failure, or irregular heartbeat
• Elderly workers, due to deteriorating respiratory, CV and immune system function
• Diabetic workers, as they may have underlying conditions such as CV disease
• ·         Pregnant workers and the developing fetus are also at risk.

Legislation MR 217/2006:

Manitoba legislation relevant to air quality includes Part 4 General Workplace Requirements (employer must ensure workplace has appropriate air quality and is adequately ventilated with prevention of contaminant accumulation), Part 6 Personal Protective Equipment, and Part 36 Chemical and Biological Substances.  Parts 6.15 and 6.16 require the employer to perform a risk assessment and provide respiratory equipment if workers are determined to be at risk, train workers properly on using respiratory protective equipment, and supply atmosphere-supplying respirators to workers entering immediately dangerous atmosphere.  Part 36 requires the employer to perform the risk assessment, develop safe work practices, train workers and ensure compliance.  Employers must determine an occupational exposure limit for airborne substance that poses a risk that doesn’t exceed the ACGIH TLV if there is one, implement regular monitoring if worker may be exposed to a concentration greater than the OEL, and implement control measures in the workplace sufficient to ensure that the exposure of the worker to the chemical does not exceed the OEL in the future.  Control measures MUST NOT include a requirement for a worker to wear PPE unless no other measure is reasonably practicable.

While part 42 – FIREFIGHTERS outlines safe work practices, the training firefighters should take, specifications for firefighting vehicle and equipment, transportation of firefighters, teamwork and suitably equipped rescue team, requirement to wear Personal Alert Safety System, there is nothing specific in this part of the WSH Regulation 217/2006 regarding air quality.  The National Fire Protection Association publishes a number of relevant standards and codes.  NFPA 1984 Standard on Respirators for Wildland Fire Fighting Operations dictates the requirement for and use of respirators for Wildland Firefighters.  There is no respirator product available that currently meets this standard.  Thus, no wildfire suppression agency in Canada is currently providing respirators as PPE for wildland firefighting. 

Protecting Workers:

Eliminating or preventing any exposure is the best way to protect health.  When employers cannot eliminate the hazard and have exposed workers, they should assess the risk, evaluate the hazard controls available and outline how they will control potential worker exposure using the hierarchy of controls

Protecting workers includes:  assessing and mitigating risk according to the hierarchy of controls with PPE as a last resort with workers using resources such as their HCPs and the AQHI to aid in prevention.

·                The plan should involve workers and should:

o   Identify workers at increased risk of exposure

o   Outline the signs and symptoms of exposure to smoke

o   Explain the hazards to workers

o   Outline what to do if a worker shows adverse symptoms suspected of being a result of smoke inhalation

o   Identify training requirements for the administrative and PPE controls chosen to mitigate the hazard

     Administrative controls

•          Check local weather forecasts and the Manitoba Sustainable Development - Fire Program website for information on fire conditions in the area.
•          Pay attention to warnings – PH warnings apply to everyone and should be followed
•         If work is not critical and can be moved to an area where AP/smoke levels are lower, consider relocating or rescheduling it when AQ conditions improve
•          Limit outdoor activities, especially if it makes workers tired or short of breath.
• Stay inside and keep windows and doors closed. Set air conditioner to “re-circulate” and keep it running to help filter the air and keep workers cool.
•         Reduce levels of physical activity, as necessary, to decrease inhaling pollutants
•          Avoid cigarette smoke or burning anything, including wood stoves, gas stoves and even candles.
•          Drivers should:
• Keep the windows closed and put the air system on “re-circulate” so smoky air doesn’t get inside
• Let outside air into the vehicle when driving through an area with low or no smoke
•          Drink water and stay hydrated to help ensure the nose and mouth are moist
•          Keep a close watch on at risk individuals, particularly those who work alone.
•          Limit any strenuous indoor activities if the worker has been exposed to smoke.
•          Turn room air cleaners with HEPA filters on.
•          Workers in Brandon or Winnipeg area should:
• Check the local AQHI for updates on air quality conditions. 
• Determine their susceptibility (at-risk)
• Should know which AQHI value affects them and self-calibrate

Personal Protective Equipment

•          When administrative controls are unable to reduce exposures to acceptable levels, respiratory protective equipment may be used and must be selected in accordance with Manitoba Regulation 217/2006 Parts 6.15 and 6.16 and the Canadian Standard Association Standard z94.4-02, Selection, Use and Care of Respirators.

•          If an exposed worker has chest tightness, chest pain, or shortness of breath, call 911 or send to the nearest emergency department right away

•          If an exposed worker has unusual tiredness, call Health Links or a HCP, even if the worker doesn’t have a history of heart or lung problems.

• Workers at risk should connect with their physician or health care provider to ensure s/he:

•          Identifies workers at risk of cardiac and/or respiratory distress during physical labour

•         Understands the worker’s work activities.
•          Evaluates and discusses the risks with the worker.
•       Educates them about early warning signs
•       Advocates regular exercise
•        Recommends maintaining fluid, carbohydrates, and electrolyte levels during a shift
•      Discourages smoking
•         Gets baseline spirometry/CXR that can be used for future reference.
•          Determines the worker’s fitness to work.
• Developed cardiavascular and respiratory disease in a worker may warrant a referral to a cardiologist, respirologist, or occupational medicine specialist.