It’s 1985, and Louis Gillete noticed that the gators of Lake Apopka, Florida were havin’ reproductive troubles. Could it be that the pesticide spill and high runoff levels have affected the crocs’ mojo?
Turns out that fertilizers with atrazine and nitrates made those poor gators’ man-parts too small and lowered their testosterone levels. What if chemicals could affect humans in similar ways?
Assesess environmental factors that –
Seeks to prevent –
influence human health and quality of life
adverse effects on human health and ecological systems
What are the four environmental hazards that threaten you and me?
(living next to toxic waste, smoking, poor diet, socioeconomic status,etc.)
Disease is a big deal to environmental health scientists:
Major killers like cancer, heart disease, and respiratory diseases are influenced by environmental factors.
(Think asthma and air pollution)
Some things that cause illness:
lack of exercise
Environmental hazards are indoors and outdoors
Basically, they’re EVERYWHERE
Indoor can include radon, lead poisoning, and asbestos.
What the heck are PBDEs?
Oh, polybrominated diphenyl ethers
A particular combo of chemicals that have been shown to affect the thyroid hormones in animals, and they’ve been banned in Europe
Toxicology is the study of poisonous substances. . .
Like Britney Spears
Toxicant: the toxic agent – Britney
Toxicity: degree of harm it can inflict – how much harm could the crackhead potentiallyinflict on her child?
“the dose makes the poison” – a little Britney here and there is okay, too much is deadly
Environmental toxicology includes toxins created by or disposed in the environment and its effects on human and animal life and ecosystems
Toxic agents are ubiquitous. . .
. . .a big word that means they are infused in everything.
We all have traces of numerous industrial chemicals in our bodies, and many of these chemicals have not been tested.
Rachel Carson is a big deal. She wrote Silent Spring, a book about DDT and artificial pesticides. She showed the country how these chemicals harm people, animals, and the environment.
The U.S. still exports DDT to other countries, but before you get your panties in a wad, let me explain why this is okay. In countries where mosquitoes carry malaria, DDT can be used to kill off the diseased pests. Wide-spread Malaria is more detrimental than the environmental effects of DDT.
What are the six types of toxicants?
Carcinogens: types of radiation that cause cancer
Mutagens: mutate the DNA of organisms
Teratogens: cause harm to the unborn
Neurotoxins: assault the nervous system
Allergens: overactivate the immune system
Endocrine disruptors: interfere with endocrine system
The 1996 book Our Stolen Future showed us that synthetic chemicals can alter animal hormones negatively.
We now believe Endocrine disruption may be widespread.
A common endocrine disruptor feminizes male animals – like those poor male alligators.
Scientists say the striking drop in male humans’ sperm counts could be due to endocrine disruptors.
Many everyday plastic products have bisphenol-A in them. This same chemical caused birth defects in lab rats. Yet the plastic industry defends their product claiming that it is safe.
What do these manufacturers want?
Dangers about toxicants in water:
1. They are soluble and therefore ingested by animals that live in the water (frogs, fish, etc.) – this is why these animals are great indicators of pollution
2. The toxicants usually travel from large bodies of water to shallower and more concentrated spots where they can do more damage.
Airborne toxicants travel like planes –
they travel in the air, and are therefore very widespread
Do toxicants live a short or long life?
A little of both: some like DDT and PCBs live long lives, while others like Bt toxin have a short persistence.
Are toxicants okay after they breakdown?
No. In fact, some are worse after breaking down. For example, DDT breaks down into DDE, which is even more highly toxic. AH.
Toxicants travel through animals by the food chain almost like STDs travel through people. Let me explain. . .
Some polar bears in Artic Norway are suffering from PCB and their cubs are dying. This is because when fish ingested the toxicant it was stored in their tissues – this is called bioaccumulation. Then the bears ate the fish and the toxicant traveled up the food chain – this process is called biomagnification. Or maybe someone just put PCB in the polar bear’s Coca Cola.
So guess what. Not all toxicants are synthetic, or created by us.
Some toxicants are purely natural. Scientists aren’t sure what kinds of risks are posed by natural toxicants. It’s a mystery.
What are four areas of studying hazards?
Wildlife – careful observations in the field and the lab
Human – direct study and treatment of individuals
Epidemiological – comparing large-scale groups of people/social epidemics
Manipulative experiments – exposing animals to potential hazards in order to determine causation
standard method of testing lab animals in toxicology
How is the response of dose-response testing quantified?
By the proportion of animals the dose negatively affects
The amount of toxicant that it takes to kill half the population of tested animals
Amount of toxicant that it takes to AFFECT (not kill) 50% of the population of lab animals
You would think more of a toxicant would mean more of a response – but, some toxicants reach their threshold dose and the response is the same above that dosage
Curves are created to show dose-response analysis. They come in a few shapes:
Some dose-response curves are U-shaped,
J-shaped, or shaped like an inverted U; these curves appear to apply to endocrine
What’s the difference between acute and chronic exposure to hazards?
1. The toxicity of many substances varies according to whether the exposure is in high
amounts for short periods of time—acute exposure—or in lower amounts over long
periods of time—chronic exposure.
2. Acute exposure is easier to recognize but chronic exposure is more common, and is
more difficult to detect and diagnose.
What is it called when multiple hazards occur at the same time and also create a reaction that is greater than the simple sum of their parts?
Risk of hazards are measured for Policy in terms of probability –
The probability depends on the toxin, its strength, the frequency and duration
of the encounter, the sensitivity of the organism, and other factors.
Our perceptions about risk related to hazards are not always true. This is why we have. . .
Risk assessment: The quantitative measurement of risk and the comparison of risks involved in different
activities or substances together
Risk Management looks at risk through a larger lens.
Scientific assessments of risk are considered in light of economic, social, and political
needs and values. Costs and benefits are hard to determine because the benefits are usually economic while the costs are usually pertain to health.
Two approaches to determining safety:
1. Innocent-until-proven-guilty approach. Problem is, this often gives way to harmful technological developments. It’s a reactive approach.
2. Harmful-until-proven-innocent approach. Assuming its all bad until proven otherwise. oftten impedes technological advances.
European countries use the precautionary approach to safety determination.
The U.S. uses the innocent-until-proven-guilty approach. Several federal agencies track and regulate these sythetic chemicals.
What did the Toxic Substances Control Act
(TSCA) of 1976 do for toxicology?
It was the first law to require screening of substances before they entered the
marketplace. But, many public health and environmental advocates view TSCA as too weak.
The Stockholm Treaty is an international convention that will outlaw what when it is ratified?
The “dirty dozen”, twelve persistent organic pollutants (POPs)
International advancement: REACH a program that. . .
(Registration, Evaluation, Authorization, and Restriction
of Chemicals) program shifted the burden of testing chemical safety from national
governments to industry.