Kukor Lect 1_What is Enviro Toxicol

7/31/2019 Kukor Lect 1_What is Enviro Toxicol

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What is environmental toxicology ?

ecotoxicology

Definition: study of impacts of pollutants on the

structure and function of ecosystems

manmade poisonous chemicals and their effect on theenvironment

does not include the study of naturally occurring toxins, forexample cholera toxin, or brevitoxin


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Environmental toxicology is a new discipline that grew out ofstudies on the environmental fate and transport of pesticides inthe 1940s and 1950s

The discipline toxicology is as old as medicine many toxic

plant chemicals are used as therapeutic agents in medicine.

The term ecotoxicology appeared in the literature in 1969

Field was pioneered by Rachel Carson


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Environmental toxicology is highly interdisciplinary field


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Rachel Carson

1907-1964 Marine Biologist from Pennsylvania

MA from Johns Hopkins U.

Author of Silent Spring

Received much attention, because she wrote

and presented scientific facts well

She was disturbed by the widespread and indiscriminate use ofpesticides

Many of these pesticides were known to affect wildlife e.g. kill birds

She lobbied very hard to control and ban certain highly toxicchemicals

Testified before congress in 1963 and called for new policies withrespect to human health and the environment


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Environmental toxicology is driven by legislation

National Environmental Policy Act

Clean Air Act

Federal Environmental Pesticide Control Act

Federal Water Pollution Control Act

Safe Drinking Water Act

Toxic Substances Control Act

Resource Conservation and Recovery Act

Comprehensive Environmental Response, Compensation and Liabilities Act

Clean Water Act


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First piece of environmental legislation was the NationalEnvironmental Policy Act 1970

Created the EPA Initially 5000 employees (1970)

Budget of 1.3 B

In 1995 there were >18,000 employees, budget of 7.2 B

USA is divided into 10 management regions

Clean Air Act Also in 1970

Required the EPA to set standards

EPA in charge of controlling mobile and stationary emissionssources

EPA controls hazardous pollutants

Amended in 1977 to set compliance standards

Amended again in 1990 to regulate acid rain and CFC emissions


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Federal Environmental Pesticide Control Act 1972

amended to FIFRA Federal Insecticide, Fungicide, and

Rodendicide Act Required manufactures to provide PMNs (Pre Manufacture

Notice) with toxicological information to register a pesticide

Sets up system of tiered toxicity testing mechanism, mesocosmexperiment, field test

Federal Water Pollution and Control Act 1972

Provided sewage treatment plant grants for many municipalities

Set effluent limits based on technology standards

Toxicity testing is used to set maximum allowable concentrationsof toxicants in discharges and receiving waters

Goal was to have all water fishable and swimable by 1983

Established goal to eliminate pollution discharges by 1985


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Safe Drinking Water Act 1974

Set mandatory drinking water standards

Controlled underground injection of wastes (aquifer protection) Amended in 1984 to set a schedule for establishing drinking

water standards for 80 chemicals (provides notice to consumers)

Toxic Substances Control Act 1976

Regulated the use of chemicals in manufacturing and production

Goal was to characterize the human health and environmentalimpact of EVERY chemical manufactured in the USA

EPA has only 90 days to review the PMN to evaluate data

Because there are thousands of chemicals produced in the USAevery year, QSAR models or rapid throughput assays are usuallyused


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Resource Conservation and Recovery Act 1976

Controlled the disposal of solid waste

Set new hazardous waste regulations

Comprehensive Environmental Response, Compensationand Liabilities Act

Also known as SUPERFUND 1980

Provided funding mechanisms to clean up abandoned wastesites

Amended in 1984 to ban land disposal of hazardous waste

Amended in 1986 to include requirements for communityemergency plans and publication of corporate Toxic ReleaseInventories

Established the SBRP program to develop innovative approachesfor cleanup and assessment of hazards


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Clean Water Act

1987

sets national water quality standards

Toxicological (animal) testing of xenobiotics is federallymandated by

Federal Insecticide, Fungicide, and Rodendicide Act (FIFRA)

Federal Environmental Pesticide Control Act

Federal Water Pollution Control Act

Safe Drinking water act

Toxic Substances control Act


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Definition : XENOBIOTIC

a chemical that is foreign to the biosphere i.e. is not produced by anatural biological or abiotic source

Also called anthropogenic, man-made, synthetic, pollutant,contaminant, recalcitrant, persistent, and toxicant

Distinguishes between quantity and scale Gordon Gribble e.g.studied the natural occurrence of organohallogens (chlorbenzoatesin fungi) this is different from large scale chemical processes forthe production of PCBs

BTEX is an acronym for benzene, toluene, ethylbenzene, andxzylene natural ??


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Environmental toxicology depends on

Lab work Effects of toxicants on biochemistry and physiology

Field work Field observations of reproduction and survival in polluted vs.

non-polluted sites

Modeling of fate and transport of toxicants in theenvironment i.e. exposure and risk assessment

Static models : short term modeling of ecosystems

Strategic models : model of a specific aspect of a

system

Testable models : model makes predictions that can

be tested in the field or laboratory


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Purpose/function of environmental toxicology is to

Identify the mode / site of action of a xenobiotic

FATE and TRANSPORT / interaction of a xenobiotic with thebiosphere (including specific organisms) after it is released /pollution occurs

identify the effect the xenoboitic has on an ecosystems / higherlevel organisation e.g. loss of fertility of Alligators in Lake Apopca

Introduction ofxenobiotic

Ecosystemeffect

site ofaction

biotransformation

physiologybehavior

communityparameters

biochemistry population

dynamics


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Introduction ofxenobiotic

Ecosystemeffect

DNARNA

ReceptorsKey enzymes

Biochemical integrity

enzyme inductionGlutathione S TransferaseMixed Functional Oxidases

HydrolasesDNA repair mechanisms

Physiology, BehaviorChromosome damage

Lesions, NecrosisTumors

Teratogenic effectsBehavior, Mortality

Community structure

DiversityEnergy transfer

StabilitySuccession

Chemical parameters

Stress proteins

Metabolic indicatorsAcetylcholinesterase inhibition

Adenyl energy chargeMetallothionen production

Immuno suppression

Population densityProductivityMating success

FecundityGenetic alterations

Competitive alterations

Parameters of xenobiotic interaction with the ecosystem


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How do we measure these effect ?

Physio-chemical characteristics:

QSAR (quantitative structure activity relationship)

CH2

NH

CH

O

CH

N

O

S

CH3

CH3

COOH

CH2

O

HN

CH CH

N

O

S

HC

N

S

CH3

CH3

COOH

CH3

CH3

COOH

Estimate the contribution of portions of the molecule to physio-chemical characteristics

Ionic interactions

Hydrophobic interactions

Van der Vaals forces

Hydrogen bonding


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Abiotic environmental fate

Partitioning

Adsorption Transport/advection

PCB vs. Benzene


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Biotic environmental fate

The interaction of a xenobiotic at the site of action in an organism is oftenmolecular happenstance i.e. xenobiotic mimic compounds which are naturally

found in species that they affect hormone mimics

Bioaccumulation

The storage of a compound in fatty tissue of an animal

Result of food chain / trophic levels

Biotransformation

Metabolic processes, mainly by environmental bacteria, that alter the

structure and toxicity of a compound

Biodegradation

Breakdown of a xenobiotic to CO2 and water


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Biotic mode of action (Receptors)

Chemicals that interfere with biochemical receptor sites

Signaling

proteins in membranes

Replication

Protein synthesis

Chemicals that damage biochemical or molecular targets

DNA damage

Strange breakage

Chromosome abnormalities

Cancer

Non-genotoxic effects such as immunosuppression


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Physiological and behavioral effects

Standard tool for assessing toxicological effects on populations Tissue lesions

Tumors

Reproductive success

Population success

Population age structure xenobiotics often exert a strongereffect on juveniles => a shift in age structure might indicate that apopulation is not doing well, because it is affected by a

xenobiotic Shift in bacterial communities contamination reduces bacterial

diversity; bacterial numbers often increase because thecontaminant is food for some while it is toxic for others


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Community effects

Species diversity

Abundance Distribution

Ecosystem effects

Productivity Trophic level structure Stability

Documents

Kukor Lect 1_What is Enviro Toxicol