CH. 17 ENVIRONMENTAL HAZARDS AND HUMAN

HEALTH

Are baby bottles and food cans safe to use?

Hormones control human development. Some chemicals can mimic hormones.

An estrogen mimic called Bisphenol (BPA) can be emitted from poly carbonate found in baby bottles

This can cause developmental problems in baby boys

BPA is still being investigated as to its deadliness

Chapter 17.1What major health hazards do we face?

Risks are usually expressed as probability

A risk is the probability of suffering harm from a hazard that can cause injury, disease, death, economic loss, or damage.

Risk assessment is the process of using statistical methods to estimate how much harm a particular hazard can cause human health or the environment

Risk management involves deciding whether or how to reduce a particular risk

We face many hazards

Biological hazards – more then 1,400 pathogens can infect humans

Chemical hazards – harmful chemicals in air, and water

Natural hazards – fire, earthquakes, floods, and storms

Life Style choices – smoking, poor food choices, alcohol

Chapter 17.2What types of biological hazards do we face?

Diseases can spread from person to person

Diseases come in many forms and can be transferred form person to person in one way or another.

An infectious disease is caused when a pathogen enters the body and multiplies in its cells

A transmissible disease can be spread from person to person

A non-transmissible disease is caused by something other then a living thing and does not spread from person to person.

Infectious diseases are still major health threats

Diseases are hard to deal with, and only get harder the longer we treat them, since they develop immunities to widely used antibiotics

A large scale out break in a country is an epidemic

A large scale outbreak around the world is a pandemic

Diseases can spread through air, water, food, and body fluids

Case study-Tuberculosis

One in three people are infected with TB and one in ten will become infected with active TB

TB attacks 9 million people every year and kills about 1.8 million people

TB is perfectly treatable, but does not always show symptoms right away

A new strain of TB is on the rise called “Multi-drug resistant TB” that can not be treated, and patients must be quarantined

Individuals matter

3 students saved thousands of lives by developing a quick diagnosis for TB

Diagnosing TB used to involve having to inspect patients fecal matter, and in LDCs patients would die from TB while waiting for results

The students found that under a microscope, TB infected cells against a black background, glow white

This means TB can be diagnosed in seconds by relatively untrained employees

Science focus- Genetic resistance to antibiotics is increasing

Antibiotics treat bacterial infections. Bacteria produce astoundingly fast, which

allow them to develop resistance quickly Many viral infections are incorrectly

treated with antibiotics, which leads to increased resistance

MRSA (mersa) is a highly resistant infection, which can cause pneumonia, flesh eating wounds, and a quick death if in the blood stream

Viral diseases and parasites kill large numbers of people

Viruses evolve faster, are not affected by antibiotics, and can kill quickly

Flu is one of the most malicious viruses in existence, if left untreated it could spread around the world in a matter of days

The second biggest viral killer is the human immunodeficiency virus, or HIV, which infects about 2.5 million people each year

And in third is hepatitis B which damages the liver and kills about a million people each year.

Science focus-ecological medicine

There is an increasing number of diseases that travel from animals to people, and from the wild to the domestic world

Hepatitis B and Dengue fever moved from apes to humans, Lyme disease moved from deer to mice to humans

Ecological medicine is a new interdisciplinary field that tracks these links between humans and animals

Urban expansion has led to large areas being infected with Lyme disease

Case study – the global HIV/AIDS epidemic

HIV/AIDS by itself is not deadly, however it severely cripples the immune system

This increases lethality of TB and other infectious diseases

Its is spread from person to person through unsafe sex, and sharing of hypodermic needles

Treatments include a course of expensive antiviral drugs, that slow the progress of aids, but only end up increasing life span by about 24 years after infection, at a cost of over $25,000 per year

Case Study – Malaria, the spread of a deadly parasite

One in every five people in the world is at risk from malaria

This parasite is spread by some mosquitos, and the parasite invades and destroys red blood cells, resulting in fevers, sweats, and abdominal pain

Malaria kills around 2,700 people per day %90 of those who died are under the age

of 5

We can reduce the incidence of infections diseases

According to the WHO, the global infections diseases death rate decreased by more than two-thirds between 1970 and 2006 and is projected to continue to decrease

Also vaccinated children in LDCs increased from 10% to 90%

Important breakthroughs and developments of simple things like oral rehydration therapy have helped reduce death rates of victims

Infectious diseases have been getting more attention from research organizations in recent years

Chapter 17.3What types of chemical hazards do we face?

Some chemicals can cause cancers, mutations, and birth defects

A toxic chemical is one that can cause temporary or permanent harm or death to humans and animals

Carcinogens are chemicals, types of radiation, or certain viruses that can cause or promote cancer

Mutagens are chemicals or forms of radiation that cause or increase the frequency of mutations, or changes in the DNA molecules found in cells

Teratogens are chemicals that cause harm or birth defects to a fetus or embryo

Case Study- PCBs are everywhere

PCBs are a class of more than 200 cholorine-containing organic compounds that are very stable and nonflammable

They exist as oily liquids, or solids that can enter the air as a vapor

PCBs were banned by congress after it was found they could lead to liver cancer

PCBs will harm us for a while yet, as they have entered the air, ground, and water, and are fat soluble, and therefore bio magnify through food chains

Some chemicals may affect our immune and nervous systems

Studies have begun to show that long term exposure to certain chemicals can harm our immune system

Some chemicals weaken the bodies immune system, and leave our bodies vulnerable to attack

Neurotoxins can harm the human nervous system

The effects of this damage include change in behavior, retardation, learning disabilities, ADD, paralysis, and death

Science focus- Mercury's Toxic effects

Mercury and all its compounds are highly dangerous

Research shows that long term exposure can permanently damage the nervous system

Mercury is released into the air from rocks, soil, and volcanoes and by vaporization from the ocean

We can be exposed to mercury through inhaling vaporized fumes, eating contaminated fish, or eating high fructose corn syrup

Some chemicals affect the human endocrine system

The endocrine system is a network of glands that release tiny amounts of hormones into the body

Hormones control sexual reproduction, growth, development, learning ability, and behavior

Some chemicals mirror the shape of hormones, and incite reactions from the body as if the body was responding to the hormone, these are called Hormonally active agents

These are sometimes called gender benders because of their impact on sexual development

Chapter 17.4How can we evaluate chemical hazards?

Many factors determine the harmful health effects of a chemical

Toxicology is the study of the harmful effects of chemicals on humans and other organisms

Toxicity is a measure of the harmfulness of a substance

Dose is the amount of a harmful chemical that a person has ingested, inhaled, or absorbed through the skin

Response is the damage to health resulting from exposure to a chemical

Case Study- protecting children from toxic chemicals

In 2005 a study of chemicals in umbilical cord blood showed of 287 chemicals, 180 found in the blood were shown to cause cancers in humans or animals, 217 have damaged the nervous systems in test animals, and 208 have caused birth defects in test animals

It is unknown what damage, if any, is caused by minute amounts of these chemicals in infants blood

More recent scientific findings suggest that the increase of the chemicals in infants has led to the increase in Autism, childhood asthma, and learning disorders

In 2009 researchers found a connection between exposure to air pollutants from pregnant women and lower IQ scores in their children as they grew

Scientists use live laboratory animals, and non-animal tests to

estimate toxicity The most common way to measure toxicity is to

expose a population of live laboratory animals to measured doses of a specific substance under controlled conditions

Mice and rats are used, because as mammals, their systems function closely to humans

Scientists expose populations to various doses and plot the responses on a dose-response curve

Some chemicals can be extremely toxic, leading to death in low doses, and some chemicals can be essentially non-toxic leading to survival in even extremely high doses

There are other ways to estimate the harmful effects of chemicals Scientists use case reports, usually made by physicians, which

provide information about people suffering from adverse effects from exposure to a chemical

Case reports are not always reliable because they do not contain information on dosage, and the person’s involved health

Epidemiological studies are useful because they compare the health of people exposed to a particular chemical, with the health of a similar group of people not exposed to the agent

However in epidemiological studies in many cases too few people have been exposed, the studies usually take a long time, closely liking an observed effect with exposure to a particular chemical is difficult and forth, we cannot sued epidemiological studies to evaluate hazards from new technologies, or chemicals to which people have not yet been exposed.

Are trace levels of toxic chemicals harmful?

Almost everyone is exposed to potentially harmful chemicals that have built up to trace levels in their blood

The U.S. geological survey found that 80% of U.S. streams and almost one-fourth of the groundwater that it sampled was contaminated with trace amounts of medications

It is hard to be concerned about these findings because in reality, we have no idea what the effect of any of these chemicals truly are

Chemists are now able to detect even smaller amounts of toxic chemicals in systems, but this may cause the illusion of increasing pollution, when in reality the pollutant may have existed there for a long time

Why do we know so little about the harmful effects of chemicals?

All methods of estimating toxicity have serious limits

However these methods are all we have Only about 10% of the 100,000 synthetic

chemicals in commercial use have been screened for toxicity

And only 2% of those have been accurately tested to determine whether they are carcinogens, mutagens, or teratogens

How far should we go in using pollution prevention and the precautionary principle?

We know little about the chemicals in and around us, and estimating their effects is difficult, time-consuming, and expensive, so where does that leave us?

Scientists in Europe are pushing for enforcement of pollution preventing

Pollution prevention is a way of implementing the precautionary principle

However, there is a question as to how far we should take this principle. By enforcing it more, we make innovators bare the burden of finding out how safe their inventions are

Individuals matter – Ray Turner and his refrigerator

CFCs can destroy the ozone, which is necessary for life on Earth

Many companies use CFCs in their manufacturing, for various purposes

Ray Turner was bothered by his companies use of CFCs to clean oxidation off of motherboards

He found that lemon juice removed this layer, and now his company runs better then ever

Chapter 17.5How do we perceive risks and how can we avoid the worst of them?

The greatest health risks come from poverty, gender, and lifestyle choices

Risk analysis involves identifying hazards and evaluating their associated risks

Statistical probabilities based on past experience, animal testing, and other research are used to estimate risks from older technologies and chemicals

The greatest health risk is poverty, malnutrition, increased susceptibility to normally nonfatal infections diseases and often-fata infections diseased transmitted by unsafe drinking water lead to this higher death rate

After poverty and gender, the greatest risk of premature death result form lifestyle choice that people make

Case Study – Death from smoking

Cigarette smoking is the world’s most preventable major cause of suffering and premature death among adults

In 2007 the WHO estimated that tobacco use contributed to the premature deaths of 100 million people during the 20th century

The WHO estimates that smoking leads to about 5.4 million deaths per year

Smoking has also been found to increase risk of dementia and Alzheimer's disease

Estimating risks from technologies is not easy

The more complex a technological system is, the more difficult it is to estimate the risk of using the system

With careful design, systems can have a high technological reliability

However human reliability is much lower, thus increasing risk

One way to fix this is to move more decisions to the machine’s side, however chance events can knock out systems, and no program can replace human judgement

Most people do a poor job of evaluating risks

Most people shrug off the known high risk of some activities they enjoy

Driving is one of the most dangerous things people in every country do each day

Fear can lead people to worry about uncommon risks, from the more common every day risks, thus reducing the usefulness of new technologies

Some people prefer a system where they have control, like how some people will drive long distances (where the chance of dying is 1 in 6,070) over flying (where the chance of dying is 1 in 9 million)

Several principle can help us evaluate and reduce risk

Compare risks. It is better to ask “How risky is this compared to other risks?” then just “how risky is this?”

Determine how much of a risk you are willing to accept

Determine the actual risk involved Concentrate on evaluating and carefully

making important lifestyle choices