week nine

Transport

movements of contaminants within or between environmental compartment or media

Chemical release from a source goes into an

environmental compartment (water,air, soil).

(Enviromental Compartment) Then it gets transported within

the compartment and then to another compartment (from water to soil, soil to air, soil to water, water to air).

(Environmental Compartment) Chemical may change in this

process during their time in these compartments

Fate

physical, chemical or biological transformations of contaminants in the environment

Fate and transport of chemicals is affected by their

physical-chemical properties, Ex: chemical that easily evaporates

How harmful a substance is depends on

physical-chemical properties of the substance

Volatility

How much it evaporates and the tendency for it to evaporate?

Polarity; Chemicals that are polar - they dissolve in

water because water is polar (LIKE DISSOLVES LIKE) non polar does not dissolve in water

Sodium chloride is polar and dissolves in

water

Oil is a lipid thus

they float and they are nonpolar

Dioxin is

nonpolar

Solubility

Water soluble toxins

Fat soluble toxins (lipophilic tendency)

not soluble in water but soluble in fats and lipids thus accumulating

Oxidation state

if an element is differently charged it will have different properties

Molecular weight

Heavier the molecule, less soluble in water

Consequences of lipophilic tendency

majority are organic materials

Bioaccumulation

building up over time, in individual organisms

Biomagnification

building up over time, across the levels in a food chain

Generally, higher-molecular-weight chemicals are:

More lipophilic and more persistent and Less volatile and less water-soluble

Persistence in environment

Quantified as a half-life in air, water, or soil and Affected by environmental conditions

Chemical is persistence

stays in the same form, doesn't break down chemically or physically

DDT - it does break down but it still is

dangerous, the properties do not change

environmental conditions

Sunlight, heavy metals, pH, oxygen availability and temperature, biological components

Toxicology

the science of the effects of toxic substances and of their fate and transport in the body

Ecotoxicology

in animal body

Environmental toxicology

studies fate and transport of the chemical before the chemical enters the body -- chemical from the source to the chemical that is in the body

Study of poisons

The science which studies toxic substances or poisons, that are substances which cause alteration or perturbation in the function of an organisms leading to harmful effects

Receptor

Organism (human) receiving exposure or dose

The human envelope

boundary that separates the interior of the body from the exterior environment → not only skin

Age

very important because it makes people more prone to exposure (elderly and young children)

General health

other illness may make one more receptive to the illness

General makeup

genetics from the family

Exposure

Contact with the human envelope - contact that is made with body (not the inner process yet)

Some chemicals can go through our skin; dimethyl mercury

went through the glove, through the skin into the blood.

Routes of exposure

Ingested (often greatest source of chemical exposure, 85%), Inhaled (air pollution, particles and volatiles, 10%), Absorbed through the skin (industrial, 5%)

Frequency of exposure

Exposure per time (month, year, day)

Exposure Assessment

Goal is to quantify exposure (or to find out Dose) - how much is in the tissue or what is the dosage

Methods draw on understanding of both

Environmental science (fate and transport of toxicants in environment)

Toxicology

(fate and transport of toxicants in the body)

Conceptual model of exposure begins with source of

exposure and concludes with toxicokinetics and effects in the body

Chemical comes close to the receptor

(microenvironment- then exposure - then absorbed dose - then biologically effective dose (not everything is biologically effective), it can be excreted through urine - this causes change in tissue structure or function - then possible health effect)

Toxicokinetics

the disposition of toxicants in the body

Quantifying exposure

Translating event of exposure into a dose estimate

Tools for area monitoring and personal monitoring

collect things from the microenvironment

Area monitoring

a filter inserted into the nozzle of a vacuum cleaner (a) collects dust to be analyzed in a laboratory

Personal monitoring

portable sampling device (b) incorporates a pump that takes a continuous air sample near the subject's breathing zone; the device also collects a sample of particulate matter over the whole period

Units of absorbed dose:

mg/(kg*day) — does not need to be milligram can be microgram - time can be day, hour, minute

Other sources of exposure info

Questionnaires, diaries; How often you travel here and there, how long do they play at the

other sources of exposure info; Surrogate measures

Surrogate measures (measure of effect of a specific treatment that may correlate with a real)

Some chemicals can be hard to measure so you measure

another chemical that might be similar - for example; measuring hormonal changes as a result of some chemical in the body

Geographic information system (GIS)

Contaminants present in a lake, who will it contaminate

Dose; Quantification of exposure

Amount of substance a person has ingested inhaled or/and absorbed

Acute dose

refers to single dose, usually high - high single dose

Chronic dose

repeated or continuous low dose over time - longer period of time but repeated

Long term

low dose over a lifetime

Absorbed dose

quantify that passes through the human envelope

Biologically effective dose

quantity available to interact with vulnerable tissue

Actual amount that receptor site 'sees' vs. amount taken in (bioavailability factor)

Amount that causes the illness

Biologically effective dose divided by

absorbed dose gives you bioavailability factor → ranges from 0 to 1 = closer to 1 means it's very high and very toxic and then zero means that its small and less toxic

Multiple exposure (doses)

food additives, pesticides, air pollution = combined at same time - the combined effect of the chemicals can be beneficial or harmful

Chemical interaction; Antagonistic

both chemicals together are a smaller effect; if you take high dose of vitamin D it reduces cancer

Chemical interaction; Synergistic

both chemicals together are a worse effect; if you have asbestos exposure plus smoking → increases risk for cancer and lung diseases

Disposition of Chemicals in the Body; Toxicokinetics → disposition of toxicants in the body

Body burden - Absorption, Distribution, Metabolism, Storage, Excretion

Toxicodynamics

effects in the body (response)

Response

how we react to the illness/chemical

Nonspecific Response; burning

destruction of cells caused by exposure to high concentration of strong acids or bases

Nonspecific Response; Narcosis

depression in sensory activity, reversible, caused by alcohols, ethers and benzene (difficulty walking, breathing, can result in a coma)

Specific; Response

damages one specific area

Specific; Response damages include

Damage to excretory organs, Damage to respiratory organs, Damage to reproductive function, Mutagenesis , Carcinogenesis

Acute toxicity

rapid death

Result of short period of time

can even result in sudden death

Chronic toxicity

Slowly working, mixed with other illness, takes forever

DOSE MAKES THE POISON

Every chemical is harmful at some level of exposure, How much exposure causes a harmful response

What is that dosage that is enough?

different for different individuals, if you take vitamins, you take it in tablets but you also take it from food or drinks (multiple sources) thus you must be careful

Medication

there is a dosage present you can not have more than a specific amount

Something that you think is not poisonous can be poisonous in increased amounts examples;

Tylenol, Calcium, Coffee

Dose Response curves - Two key characteristics

Slope (potency of effect) and Threshold (potential for safe dose) →

LD 50

one single acute dose that causes mortality of 50% of experimental animals in the group in 14 days - anything after that does not count

Dose-Effect Curves; Essential nutrients

poor vitamin intake, you take more supplements and you don't stop but too much will cause a problem

Toxicity Testing ; Some doses are given special names

Highest non-zero dose at which no effect was observed - no observed adverse effect level (NOAEL)

Lowest dose at which an effect (some effect) was observed

lowest observed adverse effect level (LOAEL)

If a study shows both a NOAEL and a LOAEL, can infer that the threshold is

between them

Reproductive toxicity

effect on reproductive capacity

Developmental toxicity

effect on developing organism, including teratogenesis

Other Methods for Toxicity Testing

Case reports - Doctors have to study cases, Epidemiological studies - Population studies, Computer simulations - Computer tells you exposure modeling example - movement of mercury, Tissue cultures of cells and bacteria

Endpoint

physiological manifestation; first sign before the symptoms occur

Use of 'biomarkers' e.g. changes in hormone levels, protein markers, and enzyme induction - these can be indications that

a person is sick

There are also environmental biomarkers

present in soil