Ch 17: Environmental Hazards & Human Health
What is BPA? How are you exposed? What’s the risk?
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.
Hazard identiﬁcation: What is the hazard?
Probability of risk: How likely is the event?
Consequences of risk: What is the likely damage?
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*
Probability is a mathematical statement about how likely it is that harm will be suffered from a hazard
• 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.
examples: bacteria, fungi, protozoa, parasites, viruses.
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)
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.
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.
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.
Pandemic = a global epidemic such as TB or AIDS
Pneumonia & Flu (bacteria and viruses)
Diarrheal diseases (bacteria and viruses)
Hep B (virus)
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
– 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.
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 😉
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
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.
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.
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
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.*
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
= 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.
..yet, WHO estimates that only 10% of global medical research and development money goes toward preventing infectious diseases in less-developed countries.
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
– arsenic, lead, mercury, vinyl chloride, polychlorinated biphenyls
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
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.
Toxicology: the study of the harmful effects of chemicals on humans and other organisms
Toxicity: a measure of how harmful a substance is
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
**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.”*
Individual sensitivity (genetics)
Individual’s detoxification system (liver, lungs and kidneys
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.
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.
Epidemiological studies: compare the health of exposed vs. not exposed groups and test for statistical association
Precautionary principle: if there’s ANY evidence of risk, we should take action to prevent or reduce it.
– 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.*
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
■ 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.