GASES AND VAPORS thermalA 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 ‘thermal’ 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 Definition:Definition: energy that may be propagated through air or some other medium, or through a vacuum electromagnetic fundamental particles Ionizingnon- ionizingIonizing versus non- 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

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

EHS 507 Environmental exposure pathways II

.... PEOPLE...

ENVIRONMENTAL EXPOSURES INFLUENCED BY HUMAN BEHAVIOR AND THE ‘SOCIAL ENVIRONMENT’?.... and vice-versa?....