Text B. Ecological surprises: the law of unintended consequences

 

Malaria once infected nine of every ten people in North Borneo, now known as the eastern Malaysian state of Sabah. In 1955, the WHO (World Health Organization) began spraying the island with dieldrin (a DDT relative) to kill malaria carrying mosquitoes. The program was so successful that the dreaded disease was nearly eliminated. Then unexpected things began to happen.

The dieldrin also killed other insects, including flies and cockroaches living in houses. The islanders were happy. Next, small insect-eating lizards that also lived in the houses died after gorging themselves on dieldrin-contaminated insects.

Cats began dying after feeding on the lizards and after licking the DDT residue off their paws and fur. In the absence of cats, rats flourished and overran the villages. When the people became threatened by sylvatic plague and typhus carried by rat fleas, the WHO parachuted healthy cats onto the island to help control the rats. Operation Cat Drop worked.

But then the villagers’ roofs began to fall in. The dieldrin had killed wasps and other insects that fed on a type of caterpillar that had either avoided or was not affected by the insecticide. With most of its predators eliminated, the caterpillar population exploded, munching its way through its favorite food: the leaves used to thatch roofs.

Ultimately, this episode ended well: both malaria and the unexpected effects of the spraying program were brought under control.

Nevertheless, this chain of unintended and unforeseen events emphasizes the unpredictability of using insecticides. It reminds us that when we intervene in nature, we can never do just one thing, and we need to ask, “Now what will happen?”

3. Use the material from Text A, Text B and additional sources from the Internet and have a round-table discussion on the following topic: ‘ What happens when people substitute technology for nature’s services?’

Additional reading

 WHY IS INDOOR AIR A CONCERN?

1. Which in your opinion is more dangerous for human health - indoor or outdoor air pollution? Read the text below and find out what researchers say on the subject.

In developing countries, the indoor burning of wood, charcoal, dung, crop residues, coal, and other cooking and heating fuels in open fires or in unvented or poorly vented stoves exposes people to dangerous levels of particulate air pollution. According to the World Health Organization (WHO) and the World Bank, indoor air pollution is the world’s most serious air pollution problem, especially for poor people.

Indoor air pollution is also a serious problem in developed areas of all countries, mostly because of chemicals used in building materials and products.

EPA studies have revealed some alarming facts about indoor air pollution. First, levels of 11 common pollutants generally are two to five times higher inside U.S. homes and commercial buildings than they are outdoors, and as much as 100 times higher in some cases. Second, pollution levels inside cars in traffic-clogged urban areas can be up to 18 times higher than outside levels. Third, the health risks from exposure to such chemicals are magnified because most people in developed urban areas spend 70–98% of their time indoors or inside vehicles.

Indoor air pollutants in homes can include radon, secondhand smoke (also called environmental tobacco smoke), carbon monoxide, nitrogen dioxide, formaldehyde, pesticides, lead, volatile organic compounds, particulate matter, mercury, sulfur dioxide, dust, and asbestos.  

Biological contaminants in homes include bacteria, molds, mildew, viruses, animal and pet dander, dust mites, cockroaches, and pollen. Standing water, water-damaged materials, and wet surfaces can serve as breeding grounds for mold, mildew, bacteria, and insects. Biological contaminants may also be found on pets and in dirty air conditioners or humidifiers, unventilated attics, laundry areas with unvented dryers, and heating and air conditioning systems.

Combustion sources include stoves, furnaces, and space heaters that use oil, natural gas, kerosene, coal, or wood. Other combustion sources are leaking chimneys and furnaces, gas water heaters and clothes dryers, fireplaces, auto exhaust from garages, and tobacco. Indoor air contaminants from combustion sources are primarily released from malfunctioning or improperly vented heating devices.  

Building materials and furnishings that may cause indoor air pollution include insulation, wet or damp carpet, floor tiles, lead-based paint, mercury-containing latex paint, hardwood plywood paneling, and furniture made of certain pressed wood products.

Household products that may cause indoor air pollution include solvents, varnishes, waxes, paints, draperies, glues, adhesives, cleaning and maintenance products, air fresheners, moth repellants, dry-cleaned clothing, personal care items, hobby supplies, and stored fuels and automotive products.

“Building-related illnesses” are diseases or illnesses that can be traced to specific airborne pollutants within a building. They include asthma, hypersensitivity pneumonitis and humidifier fever, a flu-like illness related to exposure to bacteria and fungi found in humidifiers, air conditioners, and aquariums.

Long-term health effects of indoor air pollution include respiratory disease, heart disease, and cancer. Several indoor air pollutants are known or reasonably anticipated to be carcinogens because they cause cancer.

Short-term health effects of indoor air pollution include allergic, infectious, and toxic reactions such as watery eyes, runny nose, itching, coughing, difficult breathing, headache, dizziness, nausea, vomiting, rashes, fever, and fatigue. Health problems associated with dampness, biological contaminants, and mold include asthma, allergies and hypersensitivity pneumonitis.

So far, little effort has been devoted to reducing indoor air pollution even though it poses a much greater threat to human health than does outdoor air pollution.

(http://toxtown.nlm.nih.gov/text_version/locations.php?id=136)

 

2. Work in pairs. Pick out from the text 5 words or word-combinations that can be considered active vocabulary on the topic ‘Ecology’, prepare an exercise with them and teach this vocabulary to your group.

3. Evaluate the following statements:

1) We should not get worked up about exposure to toxic chemicals because almost any chemical, at a large enough dosage, can cause some harm.

2) We should not worry much about exposure to toxic chemicals because, through genetic adaptation, we can develop immunity to such chemicals.

3) We should not worry much about exposure to toxic chemicals because we can use genetic engineering to reduce our susceptibility to the effects of toxic chemicals.

4) We should not worry about exposure to most of these chemicals because it has not been absolutely scientifically proven that they have killed anyone.

 

4. You can reduce your exposure to indoor air pollution. Which three of these actions do you think are the most important? Why?

· Test for radon and formaldehyde inside your home and take corrective measures as needed

· Do not buy furniture and other products containing formaldehyde

· Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides

· Test your house or workplace for asbestos fiber levels

· Do not store gasoline, solvents, or other volatile hazardous chemicals inside a home or attached garage

· If you smoke, do it outside or in a closed room vented to the outside

· Make sure that wood-burning stoves, fireplaces, and kerosene and gas-burning heaters are properly installed, vented, and maintained

· Install carbon monoxide detectors in all sleeping areas

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