Environmental Health

Air pollution Week 8

C&D Chapters 15, 24 and 28

What is air pollution

The result of emission into the air of hazardous substances at a rate that

exceeds the capacity of natural processes in the atmosphere to

convert, deposit, or dilute them…

Factors that affect air pollution

• Emissions (traffic, industrial, domestic)

• Geography (terrain)

• Weather conditions (rain, winds, humidity)

• Season

• Time of day

• Population density

• Indoor vs outdoor

Types of air pollution Aerosols

– Particulates solid phase• Dust• Ash• Fumes

– Solid and liquid• Smoke (from combustion)• Coastal aerosols

– Liquid – Aggregate gases (sulfate, nitrate)

GasesCOxSOxNOxPAH

Six primary or “criteria” air pollutants

• Carbon monoxide (CO)

• Ozone (O3)

• Nitrogen dioxide (NO2)

• Sulfur oxides (SOx)

• PM2.5 and PM10

• Lead (Pb)

Types of air pollution

• Individual pollutants• Reducing pollution (SO2)

– Acid rain (fog)– Corrosive, eroding

• Photochemical pollution– Aldehydes, electrophilic HCs– Oxidative, carcinogenic?

• Mixtures and complex patterns

Types of Exposures:

ContinuousRepeated

LowHigh (acute)

Respiratory response (endpoints):

Macroscopic (e.g. coughing, FEV)

Histological

Marked variability in responses - susceptibility

Combustion pollutants

• VOCs

• NOx

• N-organics

• Halo-organics

• Metals

• CO

Sources of combustion

• Tobacco

• Power plants

• Incinerators

• Automobiles

• Industry

Diesel pollutants

• Particulate matter – C + PAHs + N-aromatics

• Gases – NOx, CO, SOx

• VOCs – formaldehyde, acrolein, aldehydes

• Respiratory inflammation• Cytotoxicity to airway cells

Outdoor air pollution

Beijing

Delhi

Outdoor air pollution

Mexico City

Santiago

Indoor pollutants• Non-specific symptoms• Household vs work space• Sick building syndrome (20% exposed)

– Cigarette smoke, combustion products– Organic offgasing (glue, fabrics, furnishings)– Biological agents (infections, allergens)– Additional factors (stress, fatigue, diet,

alcohol)

Indoor air pollution: Poor countries

In the lungs…

• Site of deposition along tract• Solubility in respiratory fluids• Reactivity with membranes• Infiltration (alveolar gas exchange)• Level of exposure• Duration of exposure• Respiratory rate• Pre existing conditions (heart, lung)

Absorption in lungs

• As gas, directly into blood stream

• As particles, deposited onto bronchiolar and alveolar surface– Uptake by phagocytosis– Trigger of inflammatory response– Trigger of allergic response– Lung tissue scaring

Basic structure of respiratory tract

Measurements of lung volume

Typical lung volume measurements from normal lung, obstructive airway disease, and restrictive lung

disease

Normal, Obstructive and Restrictive Patterns of Forced Expiration

FVC = forced vital capacity FEV1 = forced expiratory volume at 1st second of active exhalationFEF25-75 = maximal mid-expiratory flow rate FEF75 = forced expiratory flow after 75% of expelled volume

Particulate matter pollution• Properties - varied

Mixture of solid phase and absorbed materials (organic, inorganic and biological) Carbonaceous core 40-60%, C 7%

• Sources– Combustion - oil and coal

• Industry• Automobiles

– Tobacco smoke– Biomass burning– Metal smelters

NAAQS: PM10: 50ug/m3, annual

150ug/m3, 24h PM2.5 15ug/m3, annual

65ug/m3, 24h

Particulates - features• Physical size

– Large

– Small ~10um

– Fine ~2.5um

• Aerodynamic diameter (size equivalent of density=1)

– Large - local irritation (>100um)

– Inhalable (<100um)

– Thoracic fraction (<20um)• Coarse PM10 (<10um)

• Fine PM2.5 (<2.5um)

• Ultrafine (<0.1um)

• Chemical reactivity

• Shape (fibers)

• Water content

respirable

Deposition of particles in humans

Parameters influencing

particle deposition

Alveolar injury and responses

Urban Particulates

• In the <2.5um range

• Large water content, trace metals, acid gases, organic chemicals, biological

• Rather uniform distribution

• Include diesel

• In the <2.5um range

• Large water content, trace metals, acid gases, organic chemicals, biological

• Rather uniform distribution

• Include diesel

Health effects of particulate pollutants

• Eye irritation• Respiratory tract infection• Exacerbation of asthma• Bronchial irritation• Heart disease• Possibly cancer (controversial) (diesel, TiO2, talc,

carbon black, toner black)

• Elevated hospital admissions, mortality • Causation(s) not fully understood

- starting at 10ug/m3

Gaseous pollutant features

• Chemical reactivity (ozone)

• Solubility in water– Soluble

• Ambient (NOx, SOx)

• Occupational (Hydrochloric acid, Ammonia)

– Less soluble• H2S, ozone

Gas pollutants - SO2

• Properties– Reacts with H2O and forms sulfurous acid (H2SO3), which oxidizes

to sulfuric acid (H2SO4)– Chemical transformation of other pollutants– Responsible for acid rain effect

• Sources– Biomass and fossil fuel combustion– Industrial emissions, smelters

• Controls– Low-S fossil fuels (clean coal)– Emission control devices

• London fog episode (acute)

NAAQS: 0.03ppm, annual 0.14ppm, 24h

SO2 …continued

• Absorption at upper respiratory tract (sulfite, bisulfite)

• Health effects (starting at <1ppm)– Respiratory tract irritation, bronchoconstriction– Pulmonary function impairment– Increased air flow resistance– Bronchitis – Exacerbation of heart diseases

• Short acute: 2min 0.4-1ppm in asthmatics• Long term, low levels

– Impairs immune pulmonary defenses– Susceptibility to infections

Gas pollutants - H2SO4

• Product of SO2 – With metals and water --> sulf. Fly ash and acid rain

• Protonates biomolecules - membrane damage

• Bronchoconstriction

• Increased air flow resistance

• Mucus secretion protects (buffer) - nose inhalation

• Asthmatics are more sensitive

• Acidity interferes with mucociliary clearance• Chronic exposure to 100g/m3 : lower respiratory damage,

macrophage mediated

Gas pollutants -NO2

• Properties– Oxidant, less potent than O3

• Sources– NO oxidation– High To combustion (automobiles, power plants)– Indoor - kerosene, gas stoves, ETS– Silos in farming (75-100ppm)

• Health effects - starting at 1.5-2ppm– Deep lung irritant - terminal bronchioles– Alveolar cells, ciliated epithelia, Clara cells– Similar to ozone but less inflammatory (if < 2-5ppm) – Enhanced infection, suppression of macrophage action – Peaks more

NAAQS: 0.05ppm, annual

Gas pollutants - CO

• Properties– Odorless, heavier than air, stronger binder to Hb than O2

• Sources– Incomplete combustion– Traffic (inside the car, parking garages, tunnels is highest)– Inside cars = 3x urban streets, and = 5x residential streets

• Health effects– Asphyxiant– Fatigue, confusion, headaches, dizziness, cardiac function (arrhythmias,

angina)– Start at 2.5% COHb (0.5% baseline) (air level 50ppm for 90min)

2ppm COHb, no effect >5ppm COHb, cardiovascular effects

40ppm COHb, is fatal

NAAQS: 9ppm, 8h 35ppm, 1h

Gas pollutants - O3

Good O3 - stratosphere

Bad O3 - troposphere

• Properties– Short lived, highly reactive, water soluble– Scrubbed in nasopharynx– Reaches terminal bronchioles and alveoli

• Sources– Photochemical reactions

• Health effects– Degenerative lung disease– Loss of lung function

NAAQS: 0.12ppm, 1h 0.08ppm, 8h

Photochemical pollution

NO2 NO + O

O2 + O O3

O3 + NO O2 + NO2

uv

Twist:

In absence of HC- the reaction reaches equilibrium

Car emitted HC- (PAH) react with O. ….

HC- + O. Oxidized free radicals NO

NO2 + Aldehydes

O3

Balance of photochemical reaction shifts toward O3 build-up!!

Hydrocarbons shift photochemical reaction…

Photochemical pollution

uvO3

NO2

HydrocarbonsO2

O2.

O3

O .

H2O

2 (HO.)

The O3 molecule is highly reactive

• Ultimate toxicant:• No enzyme can detoxify it• Only protection: prevention of its formation

Effects of Ozone on lung function

ppb

FEV

1

0.5ml

(Kinney et.al, 1996)

0.12 - 0.4 ppm for 2-3 h FVC and FEV1

ppb ppm0.300.240.200.180.120.100.090.080.070.060.050.040.02

300240200180120100 90 80 70 60 50 40 20

LA, until 1998

US-EPA 1h aveItaly study (low exposure)

WHO 1h ave

EU 1h ave

Baseline

WHO 8h ave

US-EPA 8h ave

Effects on lung function observed

Ozone levels

LA, 1h-ave

LA, 8h-ave

Ambient O3, TSP and SO2

Aldehydes R C

Alcoxyl radical RO . (RO.)

Alkoperoxyl radical RO2. (ROO.)

Nitrous acid HONONitric acid HONO2

Hydroxyl radical HO . (HO.)

Hydroperoxy radical HO2. (HOO.)

H

O

Some nomenclature of oxidative species

Effects of O3 on proteins:

Oxidation of: • sulphydryls• amines• alcohols• aldehydes

Inactivation/inhibition of enzymes in cellular compartments

Aminoacids targets:

• cystein• methionine• tryptophan• tyrosine

Effects of O3 on lipids:

• Polyunsaturated fatty acids (PUFA): primary target of O3 peroxidation of membrane lipids• Most important mechanism of O3-induced injury

O3 + PUFA carbonyl oxideH2O

Hydroxyhydroperoxy compound

HO.

H2O2Lipid peroxidation cascade

aldehydes

Lipid fragmentationMalondialdehyde (MDA)8-isoprostaneLTB4 (PMN chemotractant)

Lipid peroxidation cascade

Effects on nucleic acids

Electrophiles react with strong nucleophilic atoms of nucleic acids

DNA + HO. Imidazole ring-opened purines or ring-contracted pyrimidines

Strand breaksBlocked DNA replication

Formation of adducts depurination (apurinic sites: mutagenic)

Effects of O3 on lung function

• Decrement of lung function (FEV1 and FVC1)

• Increased airway responsiveness (non specific)

• Increased epithelial permeability, injury and loss

• May influence allergic sensitization and responsiveness

• May increase sensitivity to infections

• Induces inflammatory reactions following injury

• Exercise increases air flow and penetration

Inflammatory oxidative burst

Three pathways of HO. generation:

• NAD(P)H oxidase • Nitric oxide synthase (NOS)• Myeloperoxidase (MPO)

HO.

NAD(P)H + O2 O2.

NAD(P)+H+

Fenton

HOOH + H+ +Cl- HOClMPO

Oxidase

L-arginine + O2 NO.NOS

H+

NO2

.

O2

Cl-

L-citruline

H20

The lung’s defenses:

Antioxidant molecules:

ascorbic acid (vit. C) a-tocopherol (vit. E) uric acid glutathione (GSH)

Metabolic enzymes:

SOD Catalase GPX GSTs

• Hazardous air pollutants– Not included in the 6 criteria air pollutants

• Include – Organic chemicals (acrolein, benzene)– Minerals (asbestos)– PAH (benzo[a]pyrene)– Metals (Hg, Be)– Pesticides (carbaryl, parathion)

• Some are carcinogenic

Other air pollutants - HAPsOther air pollutants - HAPs

Volatile Organic Pollutants (VOCs)

• Sources: Petroleum emissions, fuel combustion, incineration, biomass burning

• Account for ~14% of all air pollution• Important factor of indoor air pollution• Types

– Aliphatic – Alcohols (ethylene glycol, MTBE)– Aldehydes (formaldehyde) – Aromatic (benzene, toluene, xylene)– Halogenated (TCE, PERC, Methylene Chloride)– Polycyclic (PAHs)– Other (Carbon disulfide)

VOCs Health Effects

• Alkanes (solvents, varnishes, lacquers)

– Irritants, lung and skin– CNS depressants, neuron degeneration,

paralysis– Pulmonary edema– React with OH radical in photochemical

pollution

• Alkenes (gasoline and aviation fuel) more reactive than alkanes - chains, oxides, halogenated HC

– CNS effects - cramps, tremor– GI tract - nausea, vomiting

VOCs Health EffectsVOCs Health Effects

Aldehydes

• Formaldehyde H2C=O– 50% of total aldehydes– Water soluble– Steep dose-effect:

0.5-1ppm: odor2-3ppm: mild irritation4-5ppm: intolerable

– Scrubbed in upper respiratory tract, but can also reach deeper

– Nasal cancer? (rodents but not humans)

• Acrolein H2C=CHCH=O– 5% of total but more irritating

Aromatic hydrocarbons (stable, persistent) - Low water solubility, volatile, flammable - Priority pollutants (EPA)

• Benzene - most basic– Carcinogen (epoxide, phenol metabolites)– CNS toxicity - narcosis– Irritation (skin, lung)

• Toluene (more lipophilic, but faster metabolism)– CNS depressant (narcosis, impaired coordination,

headaches)

• Xylene (o-, p-, m-) (very lipophilic)– CNS depressant (as above)– Blood cell damage, anemia– Irritant (skin)

VOCs Health EffectsVOCs Health Effects

Polycyclic aromatic hydrocarbons (PAH) incomplete combustion of organic materials, incineration, industry, natural processes– 16 of 126 priority pollutants– Environmental transport, accumulation– Photo - bio- degradation

• Carcinogens exposure* (metabolic activation) -• Air exposure 0.02-3ug/day• Cigarette smoke 0.1-0.25ug/cig• Unfiltered cigarettes 2-5ug/day• Vegetarian diet 3-9ug/day• Drinking water 0.2-120ng/day• Soil (urban) 0.003-0.4ug/day

VOCs Health EffectsVOCs Health Effects

* Menzie et.al. 1992, Env. Sci and Technol. Vol. 26: p.1278

NAAQS - CAA 1990

• National Ambient Air Quality Standards• ug/m3 or ppm

• National Air Quality and Emissions Trends Report

NAAQ Standards for six “criteria” pollutants

http://www.epa.gov/air/criteria.html

Pollutant Primary Stds. Averaging Times Secondary Stds.

9 ppm(10 mg/m3)

35 ppm(40 mg/m3)

Lead 1.5 µg/m3 Quarterly Average Same as Primary

0.053 ppm

(100 µg/m3)

Revoked(2) Annual(2) (Arith. Mean)

150 µg/m3 24-hour(3)

15.0 µg/m3 Annual(4) (Arith. Mean)

35 µg/m3 24-hour(5)

Ozone 0.08 ppm 8-hour(6) Same as Primary

0.12 ppm * 1-hour(7) Same as Primary

0.03 ppm Annual (Arith. Mean) ------- 0.14 ppm 24-hour(1) -------

------- 3-hour(1) 0.5 ppm(1300 µg/m3)

Particulate Matter (PM10)

Sulfur Oxides

Particulate Matter (PM2.5)

None

None

Same as Primary

Same as Primary

Nitrogen Dioxide

Carbon Monoxide 1-hour(1)

8-hour(1)

Annual (Arithmetic Mean)

*Applies only in limited areas

US Regulation history• 1947 CA - Air pollution control Act• 1955 - Truman’s Air pollution control Act• 1963 Federal - Clean Air Act (1967 am)• 1965 Federal - Motor vehicle Air pollution control Act• 1970 The Clean Air Act: national level (EPA)

– O3, SO2, NO2, CO, PM, Pb, total hydrocarbons (dropped)

• 1970 Lead is banned as fuel additive• 1990 CCA amendment: 118 chemicals, some carcinogenic

– Maximum achievable control technology– Additional risk assessment if health effects beyond the MACT level– Emission standards for motor vehicles (CO solution - MTBE new

problem)

• 1997 New standard for PM2.5

Clean Air Mercury and Interstate rules

• On March 15, 2005, EPA issued the Clean Air Mercury Rule to permanently cap and reduce mercury emissions from coal-fired power plants for the first time ever. This rule makes the United States the first country in the world to regulate mercury emissions from utilities.

• On March 10, 2005, in a separate but related action, EPA issued the Clean Air Interstate Rule (CAIR), a rule that will dramatically reduce air pollution that moves across state boundaries.

• Together the Clean Air Mercury Rule and the Clean Air Interstate Rule create a multi-pollutant strategy to reduce emissions throughout the United States.

http://www.epa.gov/air/mercuryrule/

Epi studies of air pollution

Outdoor studies predominantly– Cohort studies (Harvard six cities; American Cancer Society;

Adventist Health Study of Smog)– Biomarkers (breath, BAL, blood)– Lung function (FEV1, FVC, FEF25-75)– Symptoms (coughing wheezing, shortness of breath, cardiac

function)– Long-term/chronic (confounders)

• Retrospective• Prospective

– Time series• National Morbidity, Mortality and Air Pollution Study (NMMAPS)• Air Pollution and Health, a European Approach (APHEA)

Chronic effects of air pollution

• Los Angeles basin: “aging-like” effect on lung function• Netherlands: 12y, SO2 and PM• Rural PA: higher incidence of respiratory symptoms• Harvard Six Cities Study: >15y, 20,000 people SO2 and

PM• Overall reduced lung function, bronchitis• Cancer risk: 2000/year vs 100,000/year from smoking -

associated with PM/VOC combinations

Relative contribution of individual air pollutants to lung cancer rates after removing tobacco smoke

cancer (~85%)

PIC: products of incomplete combustion

US emissions trend for VOCs, NOx, SO2, and PM10, 1900-1990