Ch 17: Environmental Hazards & Human Health

Case Study: Are Baby Bottles and Food Cans Safe to Use? The BPA Controversy

What is BPA? How are you exposed? What’s the risk?

Bisphenol A (BPA) = an estrogen mimic that we’re exposed to in plastic. the risks are that it’s really toxic.

There is concern that bisphenol A (BPA), an estrogen mimic, can leach out
of polycarbonate baby bottles, especially when they are warmed, microwaved, or used
to hold acidic juices. In 2008, Canada became the first country to classify BPA as a toxic
substance and announced that it would ban its use in baby bottles. Some manufacturers
are no longer using polycarbonate plastic in baby bottles, in sipping cups, or in the plastic
lining of baby formula cans. But almost all food and soft drink cans are lined with a plastic
resin that some researchers believe can release BPA into the contents of the cans.

Hormone Mimics
Certain pesticides and other synthetic chemicals can act as hormone imposters that may impair reproductive systems and sexual development or cause various physical and behavioral disorders.

Risk Assessment of hazards
Risk assessment and risk management are used to estimate the seriousness of various risks and how to reduce
such risks.

Hazard identification: What is the hazard?
Probability of risk: How likely is the event?
Consequences of risk: What is the likely damage?

Risk
Comparative risk analysis: How does this risk rank against other risks?

Risk reduction: How much should it be reduced?

Risk reduction strategy: How will the risk be reduced?

Financial commitment: How much money should be spent?

Risk communication: communicating the reality of these risks to the public

*The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices*

How do we assess risk?
Risk is the probability of suffering harm from a hazard that can cause injury, disease, death, economic loss or damage

Probability is a mathematical statement about how likely it is that harm will be suffered from a hazard

Problem w/ risk management:
A major problem with risk management is that most people are not good at understanding and comparing risks. Because of sensational news coverage about the latest scare, many people worry about the highly unlikely possibility of minor risks, such as dying from a shark attack, and ignore the significant probability of harm from major risks, such as dying from a heart attack—the single leading cause of death in the United States. Thus, educating people and members of the news media about the meaning of risk assessments and about how to make risk comparisons is an important priority.

5 TYPES OF HAZARDS:
We can suffer harm from five major types of hazards:
• Biological hazards from more than 1 ,400 pathogens that can infect humans. A pathogen is an organism that can cause disease in another organism. Examples are bacteria, viruses, parasites, protozoa, and fungi.
• Chemical hazards from harmful chemicals in air,
water, soil, food, and human-made products.
(Core Case study)
• Natural hazards such as fire, earthquakes,
volcanic eruptions, floods, and storms.
• Cultural hazards such as unsafe working conditions, unsafe highways, criminal assault, and poverty.
• Lifestyle choices such as smoking, making poor food choices, drinking too much alcohol, and having unsafe sex.

Pathogen
an organism that can cause disease in another organism.
examples: bacteria, fungi, protozoa, parasites, viruses.

Most serious bio hazards we face:
the most serious biological hazards we face are infectious diseases (such as flu, aids, tuberculosis, diarrheal diseases, and malaria).

infectious disease
is caused when a pathogen such as a bacterium, virus, or parasite invades the body and multiplies in its cells and tissues.
Some examples are flu, malaria, tuberculosis, and measles.
– bacterial disease: spreads as the bacteria multiply (tuberculosis).
– viral disease: spreads as viruses take over a cell’s genetic mechanisms to copy themselves (flu or HIV)

transmissible disease
(AKA a contagious or communicable disease) is an infectious disease that can be transmitted fromone person to another. ex: flu, tuberculosis, and measles.

nontransmissible disease
Is caused by something other than a living organism and does not spread from one person to another.

Tends to develop slowly and have multiple causes. They include cardiovascular (heart and blood vessel) diseases, most cancers, asthma, diabetes, and malnutrition.
As average life expectancy increases, people are more likely to suffer and die from nontransmissible diseases such as cardiovascular diseases and cancers.

The leading cause of death is now nontrans-
missible cardiovascular disease, and the percentage of people dying from cancers is increasing in all countries.

Leading cause of death:
The leading cause of death is now nontransmissible cardiovascular disease, and the percentage of people dying from cancers is increasing in all countries.

Diseases then (1900; 1950) and Now
1900: infectious disease was the leading cause of death in the world and in the United States.

Since then, and especially since 1950, the incidences of *infectious diseases* and the death rates from such diseases *have been greatly reduced*. <-- This has been achieved mostly by a combination of: - better health care - better sanitation - the use of antibiotics to treat infectious diseases caused by bacteria - the development of vaccines to prevent the spread of some viral diseases.*As a result, average life expectancy has increased in most countries*. The leading cause of death is now nontransmissible cardiovascular disease, and the percentage of people dying from cancers is increasing in all countries.

Ways in which infectious diseases enter the human body:
Pets
Livestock
Wild animals
Insects
Food
Water
Air
Other humans

we pass it onto: babies

such infectious diseases can then be spread through air, water, food, and body fluids such as feces, urine, blood, and mucus droplets sprayed by sneezing and coughing.

epidemic
a large-scale outbreak of an infectious disease in an area or a country
Pandemic = a global epidemic such as TB or AIDS

pandemic
a global epidemic such as TB or AIDS

7 deadliest infectious diseases & how they’re passed
WHO estimates that each year, the world’s seven deadliest infectious diseases kill 12.5 million people—most of them poor people in developing countries.

Pneumonia & Flu (bacteria and viruses)
HIV/AIDS (virus)
TB (bacteria)
Diarrheal diseases (bacteria and viruses)
Hep B (virus)
Malaria (protozoa)
Measles (virus)

TB = Growing global threat
1/3 people is infected with TB and 1/10 will become sick with active TB

84% of the 1.7 million deaths occur in developing countries

Major problems are a lack of screening and control and the increase of drug resistant strains

Why is infectious disease still a serious threat if it’s been so greatly reduced since 1900 (used to be the #1 killer, but now nontransmissible/cardiovascular disease is)?
GENETIC RESISTANCE = many disease-carrying bacteria have developed genetic resistance to widely used antibiotics.
– Also, many disease-transmitting species of insects such as mosquitoes have become immune to widely used pesticides such as DDT that once helped to control their populations.

GENETIC resistance = One reason why infectious disease is still a serious threat.

emergent diseases
In recent years, several other previously unknown
diseases have received widespread media coverage. They are examples of emergent diseases that were newly discovered or were absent in human populations for at least 20 years.
– One is the West Nile virus, which is transmitted to humans by the bite of a common mosquito that has been infected by feeding on birds that carry the virus.
*but chance of getting infected w/ & killed by west nile is low 😉

Ecological Medicine:
Tracking How humans can get infectious diseases from other animals (avian flu; lyme disease; HIV; plague; hep B; african sleeping sickness) – b/c scientists believe that more than half of all infectious diseases were originally transmitted to humans by animals

60% of emerging diseases (1940-2004) were transmitted from animals to humans

scientists have identified several human practices that encourage the spread of diseases among animals and people:
– the clearing or fragmenting of forests to make way for settlements, farms, and growing cities. (ex: in the US, push of suburban development into forests has increased the chances of many suburbanites becoming infected with debilitating Lyme disease, b/c they interact w/ deer & white mice)
– The legal and illegal international trade in wild species = another important factor in the spread of these diseases.
– Global warming: warmer temps. allow diseases like malaria to move quicker from tropical to less tropical areas

ex: PBS documentary about tourists who get rare infectious diseases after visiting gorillas & bat caves in Uganda

how should i reduce my chances of getting infectious diseases..?
You can greatly reduce your chances of get-
ting infectious diseases by practicing good old-
fashioned hygiene. Wash your hands thoroughly and frequently, avoid touching your face, and stay away from people who have flu or other viral diseases.
However, it is not necessary to use antibacterial soaps, liquids, and sprays in order to avoid infectious diseases. Some health officials warn that these products may be doing more harm than good, because they can contribute to genetic resistance in infectious bacteria. Plain hand soap will do the job.

ways humans transmit HIV from one person to another:
through unsafe sex, the sharing of hypodermic needles by drug users, infected mothers who pass the virus on to their children before or during birth, and exposure to infected blood.

originally moved from chimps to humans

Globally, according to the WHO, AIDS is the number one killer of women between the ages of 15 and 49.

AIDS has reduced the life expectancy of the 750
million people living in sub-Saharan Africa from 62 to 47 years, on average, and to 40 years in the seven countries most severely affected by AIDS

The premature deaths of teachers, health-care workers, soldiers, and other young, productive adults affect the population age structures in African countries such as Botswana. These deaths also lead to diminished education and health care, decreased food production and economic development, and the disintegration of families.

What mass AIDS deaths can lead to:
Lowered life expectancy –> affects population age structures. Diminished education and health care, decreased food production and economic development, and the disintegration of families.

Malaria
About 40% of the world’s population lives in areas in which malaria is prevalent. Malaria kills at least 1 million—and perhaps as many as 2 million—people a year.

no vaccine for preventing it
– is caused by a parasite that is spread by the bites of certain types of mosquitoes.

About 90% of those dying from malaria are children younger than age 5
*Over the course of human history, malarial protozoa probably have killed more people than all the wars ever fought.*

more than 80% of people at risk of malaria live in Sub-Saharan Africa

ways to temporarily stunt malaria spread: bed nets & spraying DDT

what’s killed more people than all the wars ever fought?
malarial protozoa

bounce back of malaria
In 1950s & 60s, spead of malaria sharply curtailed b/c they drained or sprayed swamps/marshlands where mosquitoes bred, & drugs were used to kill the bacteria in victims’ bloodstreams.

but *Anopheles* mosquitoes *have* since *become genetically resistant to the insecticides* 🙁

the clearing and development of tropical forests have also augmented malaria’s spread

During this century, *climate change* as projected by scientists *is likely to spread cases of malaria* across a wider area of the globe. *As the average atmospheric temperature increases, populations of malaria-carrying mosquitoes will likely spread
from tropical areas to warmer temperate areas of the earth.*

What % of infectious diseases are passed from animals to humans?
60% of emerging diseases (1940-2004) were transmitted from animals to humans

How can we reduce infectious disease?
malaria: bed nets & DDT spraying

Solutions for Infectious Diseases:
Increase research on tropical diseases and vaccines
Reduce poverty
Decrease malnutrition
Improve drinking water quality
Reduce unnecessary use of antibiotics
Educate people to take all of an antibiotic prescription
Reduce antibiotic use to promote livestock growth
Require careful hand washing by all medical personnel
Immunize children against major viral diseases
Provide oral rehydration for diarrhea victims
Conduct global campaign to reduce HIV/AIDS

Oral rehydration therapy
helps prevent death from dehydration for victims of severe diarrhea, which causes about 1/4 of all deaths of children younger than age 5.
= Therapy that involves administering a simple solution of boiled water, salt, and sugar or rice at a cost of only a few cents per person.

– Has been the major factor in reducing the annual number of deaths from diarrhea from 4.6 million in 1980 to 1.6 million in 2008.

What was the major factor in reducing the annual number of deaths from diarrhea from 4.6 million in 1980 to 1.6 million in 2008?
Oral rehydration therapy (administering salt/water soln, which prevents dehydration from diarrhea)

Why we should care about infectious diseases in devel. countries:
More people suffer and die from these diseases than from all other diseases combined.
..yet, WHO estimates that only 10% of global medical research and development money goes toward preventing infectious diseases in less-developed countries.

Chemical hazards (& 3 major types of potentially toxic agents):
A toxic chemical can cause temporary or permanent harm or death to humans and animals
Carcinogens – promote cancer

Mutagens – cause mutations (like nitrite preservatives in processed food/wine that lead to stomach cancer)

Terotogen – cause birth defects to fetus or embryo

toxic chemical:
a chemical that can cause temporary or permanent harm or death to humans and animals
– arsenic, lead, mercury, vinyl chloride, polychlorinated biphenyls

Carcinogens
chemicals, types of radiation, or certain viruses that can cause or promote cancer*–a disease in which malignant cells multiply uncontrollably and create tumors that can damage the body and often lead to premature death. examples of carcinogens: arsenic, benzene, formaldehyde, gamma radiation, PCBs, radon, certain chemicals in tobacco smoke, UV radiation, and vinyl chloride. Typically, itll take 10-40 yrs for exposure to carcinogen to appear in cancer

Mutagens
chemicals or forms of radiation that cause or increase the frequency of mutations (changes) in the DNA molecules found in cells. Most mutations cause no harm but some can lead to cancers and other disorders. Ex: HNO2 (formed when you digest NO2 preservatives in food) –> mutations linked to stomach cancer

Teratogens
chemicals that cause harm or birth defects to a fetus or embryo
ex: ethyl alcohol – don’t drink when you’re pregnant! affects behavioral, physical, developmental problems in babies
other teratogens: angel dust, benzene, formaldehyde, lead, mercury, PCBs, phthalates, thalidomide, vinyl chloride.
Betw 2001-06, bbirth defects in Chinese soared by nearly 40%, probably from coal-power plants and industries that promote these teratogens in the atmosphere

PCBs
a class of more than 200 chlorine-containing organic compounds that are very stable and nonflammable. They exist as oily liquids or solids that, under
certain conditions, can enter the air as a vapor. Between 1929 and 1 977, PCBs were widely used as lubricants, hydraulic fluids, and insulators in electrical transformers and capacitors. They also became ingredients in a variety of products including paints, fire retardants in fabrics, preservatives, adhesives, and pesticides.
US Congress banned PCBs in 1977 bc they cause liver cancer
…Yet still, PCBs remain in our environment because they break down very slowly, meanwhile getting deposited in faraway places – *and because PCBs are fat soluble, they can biomagnify*

*As a result, PCBs are now found almost everywhere—in soil, air, lakes, rivers, fish, birds, your body, and even the bodies of polar bears in the Arctic.*: *According to the EPA, about 70% of all the PCBs made in the United States are still in the environment.*

PCBs and other persistent toxic chemicals can move through the living and nonliving environment on a number of pathways.

How can we evaluate and respond to chemical hazards? (Toxicology & Toxicity)
Scientists use live laboratory animals, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods
have limitations.

Toxicology: the study of the harmful effects of chemicals on humans and other organisms
Toxicity: a measure of how harmful a substance is

Neurotoxins
Chemicals that affect our nervous systems (brain, spinal cord, etc) – brain disabilities
PCBs = a neurotoxin
study showed that farmers exposed to a weed killer were very likely to get Parkinsons (a degenerative brain disease)

Methylmercury: super deadly neurotoxin that biomagnifies in foodchains, just like DDT and PCBs do

What level exposure (dose) of a particular chemical will cause harm? What do you need to know in order to answer this question?
Any synthetic or natural chemical can be harmful if ingested in a large enough quantity.
**But the critical question is this: *At what level of exposure to a particular toxic chemical will the chemical cause harm?* This is the meaning of the quote by the German scientist Paracelsus: *”The dose makes the poison.”*

Endocrine System
network of glands that release tiny amounts of hormones into the bloodstream

The Effects of a chemical depend on:
Dose
Age
Individual sensitivity (genetics)
Individual’s detoxification system (liver, lungs and kidneys
Solubility (water/oil)
Persistence
Biological magnification

Response
The damage to health resulting from exposure to a chemical
acute effect: an immediate or rapid harmful reaction ranging from dizziness and nausea to death
chronic effect: a permanent or long-lasting consequence (kidney or liver damage, for example) of exposure to a single dose or to repeated lower doses of a harmful substance.

What affects the level of harm caused by a chemical:
Solubility; Persistence (resistance to breakdown); Biomagnification

Using curve graphs (like hypothetical dose-response curve showing determination of the LD50, the dosage of a specific chemical that kills 50% of the animals in a test group)… why do Toxicologists use this method?
hypothetical dose-response curve showing determination of the LD50, the dosage of a specific chemical that kills 50% of the animals in a test group. Toxicologists use this method to compare the toxicities of different chemicals.

Why is it hard to estimate human exposure to chemicals and measure their effects?
Estimating human exposure to chemicals and measuring their effects are very difficult *because of the many and often poorly understood variables involved.*

2 Types of Dose-Response Curves
Scientists estimate the toxicity of a chemical by determining the effects of various doses of the chemical on test organisms and plotting the results in a dose-response curve. One approach is to determine the lethal dose—the dose that will kill an animal. *A chemical’s median lethal dose (LD50) is the dose
that can kill 50% of the animals (usually rats and mice) in a test population within an 18-day period.*

Nonthreshold (curve OR straight line) dose-reponse model: *any dosage* of a toxic chemical *causes harm* that
– *increases with the dosage.*

Threshold (straight line) dose-response: *a certain level of the chemical must be reached before any detectable harmful effects occur*, presumably because the body can repair the damage caused by
low dosages of some substances. (threshold of the chemical must be reached before any effects show)

The linear and nonlinear curves in the left graph apply if even the smallest dosage of a chemical has a harmful effect that increases with the dosage. The curve on the right applies if a harmful effect occurs only when the dosage exceeds a certain threshold level.

Which model is better for a specific harmful agent? That’s often uncertain and controversial because of the difficulty in estimating the responses to very low dosages.

Other methods for estimating harmful effects of chemicals:
Case reports: provide info about people suffering from exposure

Epidemiological studies: compare the health of exposed vs. not exposed groups and test for statistical association

What we don’t know, in terms of the effects of harmful chemicals in our households:
their LONG-TERM effects

Pollution Prevention and Precautionary Principle:
Pollution prevention (what scientists say is the best way to reduce our exposure to potentially harmful chemicals): we should not release any chemicals we suspect could be harmful.

Precautionary principle: if there’s ANY evidence of risk, we should take action to prevent or reduce it.

What’s the GREATEST RISK by FAR?
Poverty
– The high death toll ultimately resulting
from poverty is caused by malnutrition, increased susceptibility to normally nonfatal infectious diseases (such
as diarrhea and measles), and often-fatal infectious diseases transmitted by unsafe drinking water.

*The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices*

*We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices.*

Guidelines for Evaluating risk:
Compare risks
Determine how much of a risk you’re willing to accept
Determine the actual risk involved
Concentrate on evaluating and carefully making important lifestyl choices

3 Big Ideas of Ch. 17 (Enviro Hazards & human health)
■ We face significant hazards from infectious diseases such as flu, AIDS, diarrheal diseases, malaria, and tuberculosis, and from exposure to chemicals that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems.
■ Because of the difficulty in evaluating the harm caused by exposure to chemicals, many health scientists call for much greater emphasis on pollution prevention.
■ Becoming informed, thinking critically about risks, and making careful choices can reduce the major risks we face.