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Toxicology

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Page 1: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Toxicology

Page 2: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Toxicology • Toxicology- is the study of chemical Risk

• The advances of modern chemicals to improve human life have come along way– Insecticides, herbicides and fungicides.

• But, in addition to these benefits, there have been by products that do the exact opposite.

• The large number of chemicals releases into the environment raises questions about the effects on us and other organisms.

Page 3: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Types of harmful Chemicals

• There are 5 categories of harmful chemicals:– Neurotoxins– Carcinogens– Teratogens– Allergens– Endocrine disrupters

• All of these are found in pharmaceuticals;– Makes you think the next time you grab night quill

Page 4: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Types of Chemicals of major Concern

• Lead– Found in paint and gas• It’s a Neurotoxin and it impairs learning, nervous system

disorders and death

• Mercury– Fish consumption• Neurotoxin and it damages the brain, kidneys, liver and

weakens the immune system.

• Arsenic– Carcinogen. Found in ground water• Cancer

Page 5: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Types of chemical• Radon– Found in water and it’s a carcinogen• Lung Cancer

• Alcohol– In beverages it’s a teratogen• Causes fetuses with reduced fetal growth, brain and nervous

system Damage.

• Phthalates– Found in plastics and cosmetics. Its an endocrine

disruptor• Feminization of females.

Page 6: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Neurotoxins• Neurotoxins- are chemicals that disrupt the

nervous systems of animals– The purpose for this chemical is to interfere with insects

nervous system.• That is why neurotoxins are sometimes called insecticide.

• Insects and animals are highly sensitive to neurotoxins.

• Animals can be completely paralyzed, not able to get oxygen.– Lead and mercury are neurotoxins. – Lead is no longer a huge problem because of the

elimination of lead in gas and paint in the 70’s• Mercury is still a huge problem.

Page 7: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Carcinogens• Carcinogens are chemicals that cause cancer or

heightens the percentage of getting cancer• They cause cell damage which leads to the DNA to

be mutated– This causes mitosis to not shut off. This leads to

uncontrolled cell-growth • Carcinogens that causes mutations to happen to

the DNA is what's known as a mutagen.– Not all carcinogens are mutagens.

• The most well known includes asbestos, radon, formaldehyde and in tobacco.

Page 8: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Teratogens• Teratogens are chemicals that interfere with the

normal development of embryos or fetuses.– The most famous is Thalidomide.• This was prescribe to pregnant women during the late 1950s

and early 1960s to combat morning sickness• The result was 10s of thousands of mothers around the world

gave birth to defected babies.– The drug was taking of the market in 1961. – The most modern Teratogen is Alcohol. • Excessive alcohol consumption reduces the growth of the

fetus if pregnant• Damages the brain and nervous system.

– Called fetal alcohol syndrome.

Page 9: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Allergens• Allergens- are chemicals that cause allergic

reactions.– Allergens are able to cause an abnormally high

responses from the immune system.• In some cases difficulties in breathing and death.

– Generally, it causes allergic reactions in a small fraction of people. • Those that causes allergens are peanuts, milk and several

drugs like penicillin and codeine.

Page 10: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Endocrine Disruptors

• Endocrine Disruptors- are chemicals that interfere with the normal functioning of hormones.

• Endocrine are natural hormones that is manufactured in the endocrine system.– They’re released in the bloodstream in very low

concentrations.– These endocrines bind to receptors that regulates

certain functions in the body. • Releasing of testosterone and estrogen.

Page 11: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Endocrine Disruptors • Water pollution can contain certain hormones – Either from animal-rearing facilities, hormones from

human birth control pill in sewage.– Also, pesticides that mimic animal hormones.

• Scientist have found that male fish, reptiles and amphibians are becoming feminized.– These males have low sperm count, which reduces

populations within those ecosystem. – These endocrine disruptors turns testosterone into

estrogen. • This has the same effects on human males. • A higher risk of breast cancer in women.

Page 12: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Test to determine concentration of chemicals

• To assess the risk a chemical poses to an organism, scientist use certain methods.– Dose-response studies– Prospective studies– Retrospective studies

Page 13: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Dose-Response Studies• Dose-response studies expose animals or plants to

different amounts of a chemical and then observe a variety of possible responses including mortality or changes in behavior or reproduction.– These chemical amounts can be measured as

concentrations within their foods, air or water.– Also, can be measured as dose of a chemical.

• This is the amount of chemical that is absorbed or consumed by an organism.

– Most dose responses studies only last for 1 to 4 days.• This is due to the efficiency of the doses.

– Because of the short durations, they’re called Acute studies

Page 14: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Dose Response Studies• The Does-response studies usually measures the

mortality rate of the specimens. • When the data are graphed it usually forms a S-

shaped curve.– At low dosage, specimens do not die.– At slightly higher levels, few individuals die. • The dose at which an effect can be detected is called The

Threshold. • At this dosage, individuals that die are usually poor in health

or genetically not very tolerant to the chemical

– As the dosage increases, more individuals will die. – At the highest concentration, all individuals die.

Page 15: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

LD50

• A helpful measurement for comparing the harmful effects of different chemicals is the LD50– LD50- Lethal dosage that kills 50% of the specimens.

• This is important for assessing the relative toxicity of a chemical. – Scientist can determine whether a new chemical is

more or less lethal in comparison to other chemicals that are being used.

Page 16: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Test Specimens

• The amount of death that a chemical causes can differ among species and among different groups of species. – Mammals, birds, fish and invertebrates.

• Mice and Rats are used for Dose-Response studies instead of humans.– The results are than equaled to all mammals– Pigeons are used for all birds – Trout are used for all fish.

Page 17: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Dose Response Experiments• It is important to note that not all Dose response

experiments measure death as a response. – In many cases, they test other harmful effects that a

chemical might have. • Is it acting as a teratogen, carcinogen or neurotoxin that

could alter the behavior of an individual?

– These are called sublethal effects.• This is to determine the effective dose that causes 50% of

the individuals to display the harmful, but nonlethal, effect.

• This is called ED50 (Effective Dosage)

Page 18: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Testing standards• There are several agencies set up to regulate

experiments.• EPA-Environmental Protection Agency– The effects of chemicals on humans and wildlife– The Toxic Substances Control Act of 1976 gives the EPA

the authority to regulate many chemicals.• Excluding food, cosmetics and pesticides.

– Pesticides are regulated under another law.• Federal Insecticide, Fungicide and Rodenticide Act of 1996• This act states that the pesticide will not cause harm to the

environment.

Page 19: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Test Standards (Cont.) • As it was eluded at the beginning, scientist can

not test every organism.– Instead, they devised a system of testing a few species

that are thought to be among the most sensitive in the world. • Bird, mammal, fish and invertebrate.

– The theory is that if they can find a way to protect the most sensitive of animals from chemicals, then they can protect all the other types of organism.• Therefore, if any regulations that are devised to protect it

would automatically protect all other species in the group.

Page 20: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Testing Standards

• There are no groups set up for amphibians. – There were no regulations set up, yet, to regulate

amphibians and reptiles.

• Now, scientist use fish for aquatic amphibians and reptiles.

• Birds for terrestrial amphibians and reptiles. – Because amphibians and reptiles are experiencing

population declines, there’s an increased in testing these two groups as well.

Page 21: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Cont• LD50 and ED50 are used by agencies like EPA. – They can determine the concentrations in the

environment that should cause no harm. – IN order to obtained a safe concentration is by taking

the LD50 and dividing it by 10. • LD50 /10

– The logic is that if the LD50 causes 50% of death, then 10% should cause few or no animals to die.

– With humans there has to be extra care. • Humans are tested so mice and rats are you used.

– Once the LD50 or ED50 is found it is divided by 10 to determine safe concentration for rats and mice.

– Then the value is divided by 10 again because rats and mice may be less sensitive than humans.

Page 22: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Cont.

• Once that value is found, it is then divided by 10 again to ensure an extra level of caution. – IN other words, the LD50 or ED50 obtained by rats

and mice are divided by 1000 to set the safe values for humans.

• Chronic Studies– Even though some toxicology studies are only

conducted for a few days, some are conducted for longer periods of time.• These experiments are called Chronic Studies.

Page 23: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Chronic Studies

• These usually last from an organism is very young to when it is old enough to reproduce.– For some species chronic experiments can take

several months• Like fish

• The goal of chronic studies is to examine long-term effects of chemicals.– Including their effects on survival and their

impacts on reproduction.

Page 24: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Retrospective versus prospective studies.

• Another approach to certain experiments, instead of dose-response, is to examine large populations of humans or animals who are exposed to chemicals in their everyday lives. – This can determine those exposures are associated with

any health problems.

• Such investigations fall within the study of epidemiology.– Field of science that strives to understand the causes of

illness and disease in human and wildlife populations.

Page 25: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Cont.• There are two ways of conducting this type of

research:– Retrospective studies and prospective studies.

• Retrospective studies– Studies that monitor people who have been exposed to

a chemical at some time in the past.– In the studies, scientists identify a group of people who

have been exposed to a potentially harmful chemical.– Then they’re compared to a second group that was not

exposed to the chemical.

Page 26: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Retrospective studies• Both groups are then monitored for many years to

see if the exposed group experiences greater health problems than the unexposed group. – Example is an accidental release of methyl isocyanate

gas in Bhopal, India in1984.• 36,000 kg of gas spread through the city of 500,000

inhabitants. • 2,000 people dies that night and another 15,000 died later

from effects related to the exposure.

– Scientist have been monitoring two decades to determine if survivors of the accidents have developed any additional health problems over time.

Page 27: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Cont.

– The retrospective studies have found that approximately 100,000 people are still suffering illness from the accident.• Higher rates of respiratory symptoms, genetic

abnormalities, infant mortality, kidney failure and learning disabilities.

Page 28: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Prospective Studies• Prospective studies- monitor people who might

become exposed to harmful chemicals in the future. – Ex. Scientists might select a group of 1000 participants

and ask them to keep track of:• Food they eat• Tobacco they use• The alcohol they drink

– They do this for the next 40 years.

• As time passes the researchers can determine if the habits of the participants have any association with future health problems

Page 29: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Prospective studies and Synergistic interactions

• Prospective studies can be challenging.– This is because of participants habits could cause many

other health problems. • Habits could be associated with socioeconomic statuses

– This can cause synergisitc interactions• When two risks together cause more harm than one would

expect based on their individual risks. – example,. The health impact of carcinogen such as asbestos can be

much higher if an individual smokes tobacco.

– Studies of lead in children are often conducted using prospective studies. • Ex. Harvard studied the effects of lead on children’s intelligence

Page 30: Toxicology. Toxicology- is the study of chemical Risk The advances of modern chemicals to improve human life have come along way – Insecticides, herbicides

Synergetic interactions

• 276 children in Rochester, New York, were followed from 6 months to 5 years of age.– At the age of 5, children can take reliable IQ tests.

• In addition to lead exposure, the researchers also accounted for other factors that might affect childhood IQ. – Mother’s IQ