Environmental Science Chapter 10

Where on Earth are organisms exposed to unusually high amounts of toxins, and why does this occur?

in the North Pole and South Pole, because of prevailing ocean currents, as well as the fact that deposition exceeds evaporation at the poles. Once deposited, these toxins and pollutants enter the food web.

The leading cause of death in the world today is disease

Almost 75% of deaths worldwide are caused by communicable diseases (those that can be passed from person to person) and diseases with a genetic or behavioral cause (e.g., cardiovascular disease, cancer).

Why are scientists interested in the effects of environmental hazards on wildlife?

Animals can serve as an early warning to the damage of environmental toxins. Much like the proverbial canary in the coal mine, studies on wild animal populations can detect the effects of toxins on wildlife before they show up in humans.

Chronic exposure to a chemical occurs at low levels over a long period of time.

Chronic means a long time of developing a condition at low exposure over a long period of time.

Epidemiological studies are comparisons that track the fate of large groups of people for long periods of time in order to help answer an environmental question.

Epidemiological studies track the fate of exposed and unexposed groups for long periods to provide data that will allow the detection of observable differences between the groups.

Which of the following statements about the United States and Europe are true regarding toxins?

European nations tend to use the precautionary principle, whereas the United States follows the innocent-until-proven-guilty approach. In the United States, powerful corporate interests have been able to ensure that the responsibility of determining whether a chemical is safe is placed on the government instead of on the manufacturer.

Why is epidemiology important for understanding human toxicology?

Following individuals with exposure to toxicants or mutagens allows for the calculation of the rates at which health problems are likely to develop. Epidemiology is based on a large sampling of people who have been exposed to a given toxicant, mutagen, disease-causing organism, radiation, and so on.

Which one of the following United States federal agencies does NOT handle risk management decisions concerning environmental health and toxicology?

Housing and Urban Development (HUD). The types of policy decisions covered in this chapter are not part of this agency's directive covers.

Which of the following statements about biomagnification is true?

It is the increase in toxicant concentration as it moves up to the top trophic levels in the food chain. DDT (still used in Africa and South America) is more concentrated in top predators than in lower levels of the food chain (trophic pyramid).

Cigarette smoke and radon are two of the most common indoor hazards.

Most people spend upward of 90% of their time indoors. Without proper ventilation, many pollutants can accumulate indoors. Cigarette smoke and radon are the leading indoor hazards.

Which of the following is an example of synergistic effects?

Two gases chemically combine to become a different pollutant with new, unique properties.

Which term describes a type of toxicant that overactivates the immune system?

allergen. not universally considered toxins, because a given allergen will not necessarily affect any given person.

How is a dose-response curve developed?

by graphing the response of model systems or organisms to specific doses of toxicants. The response is generally quantified by measuring the proportion of animals exhibiting negative effects at a range of toxicant concentrations.

What value of LD50 indicates low toxicity?

high. The LD50 indicates the dose of a toxicant that is lethal to 50% of people. If the number is high, then a high dose of the substance is required to kill people.

Which of the following can spread quickly as a result of human mobility?

infectious diseases. Biological hazards are many times communicable and can be spread from one human to another. Because we can travel worldwide very quickly, our biological hazards can as well.

A child enters the pediatrician's office with symptoms that include anemia, hearing loss, and kidney and stomach problems. The family has recently moved into a 50-year-old home and is doing renovations. What might be the problem with this child?

lead poisoning. Many older homes have lead-based paint. When young children are exposed to lead, the symptoms described above can occur.

The precautionary principle approach to chemical testing prevents products from entering the marketplace until well tested

The main idea of the precautionary principle approach is that products go through extensive testing before being allowed to reach consumers.

If an evaluating committee places the burden of proof of the safety of a new chemical on the manufacturer of the chemical, then the committee is using the precautionary principle

The use of this principle places the responsibility of harm to the environment and humans on the manufacturer of the chemical instead of on the government.

A vector is an organism that transmits a pathogen to a host.

These organisms include rats, mosquitos, fleas, ticks, and even human beings.

How do endocrine disruptors affect human health at very low doses?

They mimic or block hormones that direct reproductive and developmental processes. Endocrine disruptors interfere with the normal hormonal communication system that controls, among other things, the normal patterns of development and reproduction. Reread the section called "Toxic substances come in different types."

Risk is determined using the statistical description called probability, which helps us to determine the likelihood of a certain event occurring.

This is a description of the likelihood of a given thing happening. This description is quantitative.

How do toxicants get transported over vast distances?

Toxicants are carried by the wind as well as the waters of streams and the oceans. Toxic substances are released into the air and can travel far from where they were manufactured or used. They can also be transported by water over large distances because of water's inherent cohesion.

In many waterways around the United States, polychlorinated biphenyls (PCBs) have contaminated the sediments and wildlife. Given that most of the PCBs in the environment were released before 1980 and are still present in these ecosystems, which of the following choices best describes this phenomenon?

long persistence. The rate at which PCBs break down in the environment is very slow.

Which types of experiments are needed to establish that a certain toxicant actually causes a particular disease?

manipulative. This type of experiment is most useful for establishing cause and effect but is often unethical to perform on humans.

Within a political context, what does risk management influence with regards to environmental health and toxicology?

policy. Policy is how management decisions based on risk assessment are implemented.

At which stage of the sequence of events is rigorous testing implemented utilizing the precautionary principle?

pre-market testing by industry, government, and academic scientists utilizing the precautionary principle approach. This is only the second stage in the sequence of events for marketing the product. Doing this saves taking any of the other steps.

Which term quantitatively describes the likelihood that you would have an effect from exposure to an environmental toxin?

probability. The risk of exposure is measured in terms of probability that those exposed will suffer a harmful outcome.

Which of the following is an example of a cultural hazard?

smoking cigarettes. This is a choice that people make that exposes them to significant health hazards.

What is a threshold dose with regards to a dose-response curve?

the dosage in which a response is first elicited. Reread the section called "Dose-response analysis is a mainstay of toxicology."

In what two ways can surface water and groundwater transmit toxins to human beings?

through drinking water and through water consumed by nonhuman biota, which, in turn, are consumed by human beings

What happens as toxicants, such as fat-soluble DDT, are taken in by organisms from the lowest trophic level to the highest trophic level?

The levels of a given toxicant increase more or less exponentially at each successive trophic level. Reread the section called "Toxic substances may accumulate and move up the food chain."

A low LD50 indicates a high toxicity

The low LD50 means that it does not take much toxicant to cause the death of 50% of the subjects exposed to it.

Living on a fault line that is prone to earthquakes is an example of a physical hazard.

Physical hazards occur naturally in the environment. Other examples include tornadoes, floods, volcanoes, and fires.

Which important environmental book exposed the hazards of using the insecticide DDT?

Silent Spring. Rachel Carson wrote this book in 1962. It exposed the dangers to birds from widespread use of DDT.

Nicotine and alcohol have been shown to be harmful to a fetus in the womb in that they can lead to birth defects. Nicotine and alcohol are, therefore, potential teratogens

Teratogens are a type of toxin that causes harm to developing fetuses.