environemntal pollutants and toxicological chem

pollutant

a substance or effect that adversely alters the environment by changing the growth rate of a species, interferes with the food chain, is toxic, or interferes with health, comfort, amenities or property values of people

which sphere is pollution the focus

anthrosphere (pertains to concerns with human activity)

surface/ groundwater contamination

pollutants flow from source to sink

atmosphere → soil → groundwater OR surface water

concerns with water quality

1. human health and welfare

2. health of aquatic ecosystems

inorganic pollutants

natural or anthropogenic sources

ex: arsenic in drink water in india and bangladesh is natural due to geological formations containing arsenic

most important difference between organic and inorganic pollutants

inorganic = can never be destroyed because they are chemically reducing elements

organic = can be broken down by various techniques such as UV light

ground water contaminants

• fertilizers/pesticides

• pharmaceuticals and their metabolites

• drugs releases through urine

Dense non aqueous phase liquid (DNAPL)

density > 1g/mL → denser than water → flows down into the water (can cause layer to form across the bottom of the water)

Light Non Aqueous Phase liquid (LNAPL)

density <1g/mL → less sense than water → floats on the surface of water (problem with diffusion and leading to volitization)

solubility

high solubility on water is most dangerous as it can be carried downstream

Kow

• inversely proportional to solubility (high Kow = not very soluble)

• high Kow is dangerous bc it can build up in tissues by easily hoping across membranes into the cell

• octanol water partition coefficient → measures ratio of how a chemical splits between oily and water environments

bio concentration factor

• the tendency for a chemical to bioaccumulate

[chemical] in organism / [chemical] in water column

sewage sludge

produced in waste water treatment and is disposed into the ocean, landfills, is incinerated or used in soil → can contain nutrients but also contains environmental pollutants

industrial waste

coal combustion fly ash (CFA) is a by product of burning coal at plants and can build up at a large scale containing high levels of contaminants that have drinking water and ecological impacts

chemical composition of coal fly ash

crystalline phase → high potential for leaching of metals (big problem)

glasseous phase → lower potential for leaching of metals

agriculture

contaminates water with fertilizer runoff causing [O2] to become too low to support aquatic life → increase numbers of dead zones

natural disasters

ex: hurricanes can rupture tanks and cause oil and chemical spills in neighborhoods

chemical disasters (man made since WW1)

1. accidents with sudden catastrophic release

2. DIRECT contamination of food and drinking water → health problems over days/weeks

3. INSIDIOUS contamination of food and water supply → health problems over months/years

worlds worst industrial disaster

india 1984 → 40 tons of CH3NCO was released when water entered the tank → exothermic reaction → increased pressure → tank ruptured and killed many due to complications of exposure

point sources

RELATIVELY EASY TO CONTROL

• landfills (emit methane)

• underground storage tanks

• septic systems

• factories, industrial and military installations

• snow dumps )contain salt with chemicals that can leach when snow melts)

non point sources

DIFFICULT TO CONTROL/HARDER PROBLEM TO SOLVE

• agriculture fertilizer

• pesticide applications

• road deicing salts

• emissions from vehicles

national reports on human exposure to environmental chemicals

~40 organic pollutants and ~10 metals detected and quantified in blood

• reports are done to see which chemicals, how much, adverse health effects,, establish reference ranges, make efforts to reduce exposure, look at which groups are exposed

• reports have seen a decrease in lead in blood since banning lead in gasoline production

toxicology

the study of harmful interactions between chemicals and biological systems

→ we need this as new chemical and existing chemicals continue to be produced at large amounts increasing exposure to all organisms

toxicologists

collect data on toxicity of compounds, gain knowledge on mechanisms used to produce toxic effects, make responsible predictions about hazards for human populations

types of toxic substances

• drugs

• food additives/contaminants

• industrial chemicals

• environmental pollutants

• natural toxins

• household poisons

drugs

have highly potent activity in biological systems, toxicity is dose dependant

→ must also consider drugs used in veterinary practice as humans can be exposed through meat consumption

example → roxarsone

a feed additive used in chickens to increase growth and egg production

→ not toxic on its own but can be converted to arsenate within 10 days when exposed to air, water, etc → chicken litter spread as agriculture fertilizer → humans exposed to arsenate

food additives/contaminants

food additives = change the colour, flavour, prevent spoilage → usually have low biological activity

contaminants = many potentially toxic substances naturally occurring in food ex: Japanese pufferfish

industrial chemicals

hazards at workplace where they are used, formulated or manufactured → exposes workers and can have long term affects (accumulation in the body over a long period of time)

environmental pollutants

from industrial processes or deliberate release into the air, ocean, rivers, land ex: pesticides and shooting ranges (pb ammunition)

household poisons

pesticides, drugs, solvents, cleaning products → can cause eye and skin irritation

example → paraquat

a herbicide that kills by interfering with photosynthesis

→ can be fatal in human poisonings involving deliberate ingestion, if not fatal causes serious lung and kidney damage

why is paraquat so toxic

• accumulates in your lungs as it has a similar structure to diamines which are naturally made in the body therefore the body lets in the toxin due to similar structure

• once in the body it builds up and at sufficient concentrations is toxic to alveolar cells (in the lungs)

acute exposure

a high dose enters the system at once (inhalation of a chemical)

chronic exposure

accumulates in your system over a period of time (exposure through drinking contaminated water)

example of Hg exposure in San Fran

wind blowing from the ocean to research site = less [Hg] in air

wind blowing from city or research site = more [Hg] in air

types of poisonings

1. accidental → usually children and elderly

2. intentional

4 phases of toxic compound disposition

1. absorption

2. distribution

3. metabolism

4. excretion

absorption

involves passage across cell membranes in order to exert toxic affect

distribution

via the blood stream by binding to plasma cells

metabolism

leads to more polar metabolite and potential molecular weight increase

excretion

through urine, feces, lungs, breast milk → molecular weight plays an important factor

cell membranes

are selectively permeable only allowing certain substances to pass through based on:

• size

• lipid solubility

• structural similarity

• polarity/charge

3 requirements for passive diffusion

the most important mechanism of absorption of toxic compounds

1. concentration gradient

2. molecule must be lipid soluble

3. molecule must be non-ionized

where are weak acids absorbed

stomach

where are weak bases absorbed

intestine

rate of diffusion

FICKS LAW → K x A (C2-C1)

where A is surface area

5 requirements for active transport

1. specific membrane carrier

2. metabolic energy for operation

3. saturable at high [substrate]

4. transport against concentration gradient

5. similar substrate may compete for re uptake

3 types of transporters/carriers

1. uniport

2. symport

3. antiport

→ 2 and 3 are cotransporters

metabolism/biotransformation reactions

get rid of foreign chemicals such as hydrophobic organic compounds, the body attaches hydrophilic groups such as glucuronide sulfate to decrease log Kow and make the compound more soluble

glutathione (GSH) conjugation

found in mM conc in all mammalian cells, reacts either chemically or enzymatically to GS conjugates to be subsequently excreted into bile by ATP pumps to be excreted from the body

types of toxic response as a result of human exposure

7 different ones (direct action, biochemical lesions, pharmacological, immmunotoxicity, tertogenicity, genetic toxicity, carcinogenicity)

direct toxic action

tissue lesions, necrosis and apoptosis

biochemical lesions

interferes with vital functions such as respiration

pharmacological/physiological

affect a particular body function such as blood pressure

immunotoxicity

immune/allergic reactions

tertogenicity

affects embryo development

genetic toxicity

causes genetic mutations

carcinogenicity

produces tumours

selective toxicity

different species of animals and cells have differences in susceptibility and reactions therefore it is hard to predict toxicity in humans using another species

why does selective toxicity exist

differences in absorption, distribution, metabolism, excretion and receptor types

examples → norbormide and penicillin

norbormide - selectively kills rats as they have a receptor in smooth muscle that humans lack

penicillin - interferes with biosynthesis of the bacteria cell wall therefore the bacteria dies if it cant form its cell wall

relationship between dose and response in toxicity

response = death (all or nothing) or pathological lesions (graded responses)

dose = mg of substance / kg body weight

*toxicity dependant on dose and structure

LD50

dose of substance that kills 50% of animals in a given time (not an exact value therefore questions usefulness)

what is LD50 used for

used as a comparison tool to get an idea of how toxic a compound is relative to others → depends on route of administration

botulinum’s toxin (protein)

produced by nature in anaerobic bacillus clostridium botulinum → caused botulism which has adverse affects to processes in the brain → one of the most potent toxins known, found in improperly canned foods

mechanism of toxicity

exposure is rarely limited to a single substance, is often a mixture and the toxicity of two compounds can either be additive, synergistic or antagonistic (detoxify each other)

antagonist example → selenite and arsenite or selenite and mercury chrloride

molecules react and have non toxic effect as they stick together so tightly when they react it cannot affect organisms

ricin

a highly toxic plant product used in intentional poisoning

→ unique mechanism → 1 molecule kills one cell by entering the cell and blocking the ribosome therefore inactivating it and killing the cell