GASES AND VAPORS

•A chemical substance where all the molecules are not connected within any sort of structure and so are free to move completely at random, colliding with one another and exchanging energy between one another (i.e., in ‘thermalthermal’ motion).

WHAT MAKES CHEMICALS IN THE ENVIRONMENT

HARMFUL? •Reactions with living cells that

may modify normal functions or otherwise cause changes, resulting in damage and structural (including DNA) defects

• CancerCancer a particular concern – but only one among many

RADIATION• DefinitionDefinition:: energy

that may be propagated through air or some other medium, or through a vacuum

• electromagnetic

• fundamental particles

• IonizingIonizing versus non-ionizingnon-ionizing

ELECTROMAGNETIC ENERGY

•Radiation in the form of ‘quanta’ emitted during energy transitions in atoms or molecules:-– at the atomic level– at the nuclear level

visible light, UV, X-rays, gamma rays.

‘PARTICLE’ ENERGY•Nuclear particles released during radioactive decay of unstable atoms (radionuclides):-–alpha-particles (2 protons, 2 neutrons = He++)

–beta-particles (1 electron)–neutrons (no charge)

WHAT MAKES RADIATION HARMFUL?

• Energy transmitted during collisions with cells may cause changes, resulting in damage and structural (including DNA) defects.

• CancersCancers a particular concern.

BIOLOGICAL AGENTS• Microorganisms

– viruses, bacteria, fungi, etc. infection, allergic reactions, etc.

• Toxins of biological origin– bites or stings inflammation,

intoxication, allergic reactions, etc.• Allergens from plants

– certain plants dermatitis, rhinitis, asthma

• Protein allergens from animals– certain animals allergic reaction

BIOLOGICAL AGENTS•Toxins

– Exotoxins•Toxins secreted by the organism

– Endotoxins• toxins produced by a microorganism

that are retained within the cell, and is released - in the form of very fine particulate matter - when the cell dies and disintegrates

Endotoxin

• A Gram-negative bacterium.   Electron micrograph of Escherichia coli (a), together with a schematic representation of the location of lipopolysaccharide (LPS; endotoxin) in the bacterial cell wall (b) and the architecture of LPS (c). provided by M. Rhode, German Research Centre for Biotechnology, Braunschweig, Germany.

WHAT MAKES BIOLOGICAL AGENTS HARMFUL?• Allergic Reactions

– Repeated exposures resulting in recognition and sensitization of the immune system to foreign substances (most often proteins) derived from microorganisms, plants, or animals

– Inflammatory response on re-exposure typically results in asthma if inhaled or dermatitis if skin contact

Dust Mite

WHAT MAKES BIOLOGICAL AGENTS HARMFUL?

• Infection– Invasion of

microrganisms in which conditions are favorable for growth, production of toxins and damage to tissue

Giardia

PHYSICAL AGENTS• Thermal stress

(‘hot’, ‘cold’)• Vibration (direct

transmission of mechanical energy)

• Noise (radiation of mechanical energy)

WHAT MAKES PHYSICAL AGENTS HARMFUL?

•Mechanical or thermal energy transmitted to cellular or larger-scale systems, resulting in damage

CLASSIFICATION OF ENVIRONMENTS

• ‘AIR’ vs ‘WATER’ vs ‘FOOD’• ‘AMBIENT/ENVIRONMENTAL’

vs ‘OCCUPATIONAL’• ‘INDOOR’ vs ‘OUTDOOR’

DISPERSAL OF CHEMICAL AND BIOLOGICAL AGENTS

• Sources– defined in terms of what is emitted

and where, and its strength• Sinks

– locations within which the agent may reside and accumulate after emission

• Receptors (or targets)– the exposed population

EHS 507

The Continuum From Emission of a Contaminant (adverse agent) to a Health Effect

Transport and

transformation

Contaminant source

emissions

Accumulation in

environment

Human contact: exposure

Potential dose to body

Early expression of

disease

Health Effect

Biologically effective dose

Internal dose

Routes of Transport

EHS 507

Environmental exposure pathways I

EHS 507

The Continuum From Emission of a Contaminant (adverse agent) to a Health Effect

Transport and

transformation

Contaminant source

emissions

Accumulation in

environment

Human contact: exposure

Potential dose to body

Early expression of

disease

Health Effect

Biologically effective dose

Internal dose

Environmental exposure pathways

EHS 507

Environmental exposure pathways II

. . . . PEOPLE . . .

ENVIRONMENTAL EXPOSURES INFLUENCED

BY HUMAN BEHAVIOR AND THE ‘SOCIAL ENVIRONMENT’?

. . . . and vice-versa? . . . .