Pest Management and Toxicology

How Can We Protect Crops from Pests More Sustainably? We can sharply cut pesticide use without decreasing crop yields by using a mix of cultivation techniques, biological pest controls, and small amounts of selected chemical pesticides as a last resort (integrated pest management).

Nature Controls the Populations of Most Pests What is a pest? Interferes with human welfare Natural enemies—predators, parasites, disease organisms—control pests In natural ecosystems In many polyculture agroecosystems What will happen if we kill the pests?

Natural Capital: Spiders are Important Insect Predators Fig , p. 297

We Use Pesticides to Try to Control Pest Populations Pesticides Insecticides Herbicides Fungicides Rodenticides Natural pesticides Herbivores overcome plant defenses through natural selection: coevolution

We Use Pesticides to Try to Control Pest Populations First-generation pesticides Borrowed from plants Second-generation pesticides Lab produced: DDT and others Benefits versus harm Broad-spectrum and narrow-spectrum agents Persistence varies

Individuals Matter: Rachel Carson Biologist Silent Spring Potential threats of uncontrolled use of pesticides

Rachel Carson, Biologist Fig. 12-B, p. 298

Modern Synthetic Pesticides Have Several Advantages Save human lives Increases food supplies and profits for farmers Work quickly For many, health risks are very low relative to benefits New pest control methods: safer and more effective

Modern Synthetic Pesticides Have Several Disadvantages Accelerate rate of genetic resistance in pests Expensive for farmers Some insecticides kill natural predators and parasites that help control the pest population Pollution in the environment Some harm wildlife Some are human health hazards

Pesticide Use Has Not Reduced U.S. Crop Losses to Pests David Pimentel: Pesticide use has not reduced U.S. crop loss to pests : crop losses from insects increased from 7% to 13%, even with 10x increase in pesticide use High environmental, health, and social costs with use Use alternative pest management practices Pesticide industry disputes these findings

Trade-Offs: Conventional Chemical Pesticides Fig , p. 299

What Can You Do? Reducing Exposure to Pesticides Fig , p. 300

Case Study: Ecological Surprises: The Law of Unintended Consequences 1955: Dieldrin (DDT relative) sprayed to control mosquitoes Malaria was controlled Dieldrin didn’t leave the food chain Domino effect of the spraying Happy ending

Laws and Treaties Can Help to Protect Us from the Harmful Effects of Pesticides U.S. federal agencies and laws EPA, USDA, FDA Fungicide and Rodenticide Act, 1947 – assess health risk of active ingredients in pesticide products. Food Quality Protection Act, 1996 – reduce pesticide residue on food by factor of 10 Effects of active and inactive pesticide ingredients are poorly documented U.S. exports many banned pesticides Circle of poison

There Are Alternatives to Using Pesticides Fool the pest Crop rotation; changing planting times Provide homes for pest enemies Polyculture Implant genetic resistance – genetic engineering Bring in natural enemies Predators, parasites, diseases

There Are Alternatives to Using Pesticides Use insect perfumes pheromones Bring in hormones Interfere with pest life cycle Alternative methods of weed control Crop rotation, cover crops, mulches

Solutions: An Example of Genetic Engineering to Reduce Pest Damage Fig , p. 302

Natural Capital: Biological Pest Control Fig , p. 302

Integrated Pest Management Is a Component of Sustainable Agriculture Integrated pest management (IPM) Coordinate: cultivation, biological controls, and chemical tools to reduce crop damage to an economically tolerable level Reduces pollution and pesticide costs Disadvantages Requires expert knowledge High initial costs Government opposition

Core Case Study: Are Baby Bottles and Food Cans Safe To Use? The BPA Controversy Some synthetic chemicals act as hormone mimics and disrupt the human endocrine system Excess estrogen effects on males Feminization Smaller penis Lower sperm counts Presence of both male and female sex organs

Core Case Study: Are Baby Bottles and Food Cans Safe To Use? The BPA Controversy BPA (bisphenol A) Estrogen mimic In polycarbonates and other hardened plastics Baby bottles and sipping cups Reusable water bottles Sports drink and juice bottles Microwave dishes Food storage containers Liners of most food and soft drink cans

Core Case Study: Are Baby Bottles and Food Cans Safe To Use? The BPA Controversy BPA leaches into foods and drinks Even when containers not heated 93% of Americans older than 6 have BPA levels above the threshold level set by the EPA Higher in children and adolescents Risks for infants, children, adults

Baby Drinking from BPA Bottle Fig. 17-1, p. 436

What Major Health Hazards Do We Face? We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices they make.

Risks Are Usually Expressed as Probabilities Risk Probability of suffering harm from a hazard Probability vs. possibility Risk Assessment Risk Management

Science: Risk Assessment and Risk Management Fig. 17-2, p. 437

We Face Many Types of Hazards 1.Biological: Pathogen: an organism that causes disease in other organisms 2.Chemical 3.Physical 4.Cultural 5.Lifestyle choices

What Types of Biological Hazards Do We Face? The most serious biological hazards we fade are infectious diseases such as flu, AIDS, tuberculosis, diarrheal diseases, and malaria.

Some Diseases Can Spread from One Person to Another Infectious disease Pathogen invades the body and multiplies Transmissible disease Contagious or communicable disease Infectious disease transmitted between people Flu, tuberculosis, measles

Some Diseases Can Spread from One Person to Another Nontransmissible disease Not caused by living organisms Heart disease, most cancers, diabetes Since 1950, death from infectious diseases have declined due to Better health care Better sanitation Antibiotics Vaccines

Infectious Diseases Are Still Major Health Threats Infectious diseases spread through Air Water Food Body fluids Epidemics and pandemics Resistance of bacteria and insects to drugs and pesticides

Science: Pathways for Infectious Diseases in Humans Fig. 17-3, p. 439

Major Causes of Death from Infectious Diseases in the World, 2007 Fig. 17-4, p. 439

Science Focus: Genetic Resistance to Antibiotics Is Increasing Bacteria: rapid reproduction, easily spread Overuse of antibiotics Overuse of pesticides

Science Focus: Genetic Resistance to Antibiotics Is Increasing Methicillin-resistant Staphylococcus aureus (MRSA) Resistant to most antibiotics Symptoms of MRSA How will it be controlled?

Case Study: The Growing Global Threat from Tuberculosis One in ten will become sick with TB 1.8 million deaths each year, primarily in less-developed countries Why is tuberculosis on the rise? Not enough screening and control programs Genetic resistance to a majority of effective antibiotics Person-to-person contact has increased AIDS individuals are very susceptible to TB

Lung Tissue Destroyed by Tuberculosis Fig. 17-5, p. 440

Individuals Matter: Three College Students Have Saved Thousands of Lives North Carolina State seniors Developed a device that can detect TB bacteria on a slide Very useful in less-developed countries

Viral Diseases and Parasites Kill Large Numbers of People Influenza or flu virus #1 Killer HIV #2 Killer Hepatitis B virus (HBV) #3 Killer Emergent diseases: West Nile virus

Viral Diseases and Parasites Kill Large Numbers of People Viruses that move form animals to humans West Nile virus Ecological medicine Reduce chances of infection: 1.Wash your hands 2.Avoid touching your face 3.Avoid sick people

Science Focus: Ecological Medicine: How Humans Get Infectious Diseases from Animals Ecological medicine Human practices that encourage the spread of diseases from animals to humans Emerging infections HIV Avian flu Hepatitis B Lyme virus

Case Study: Global HIV/AIDS Epidemic Acquired immune deficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV) Many secondary infections No vaccine to prevent or cure AIDS Expensive drugs—live longer

Case Study: Global HIV/AIDS Epidemic 25 million deaths, so far #1 killer globally of women Most prevalent in sub-Saharan Africa Life expectancy dropped from 62 to 47 Alters age structure of population

Case Study: Malaria — The Spread of a Deadly Parasite Malaria Caused by Plasmodium sp. carried by Anopheles mosquitoes Tropical and subtropical regions Spread Symptoms Malarial cycle

Case Study: Malaria — The Spread of a Deadly Parasite Malaria on the rise since 1970 Drug resistant Plasmodium Insecticide resistant mosquitoes Clearing of tropical forests AIDS patients particularly vulnerable Prevention of spread and current research

Global Outlook: Distribution of Malaria Fig. 17-6, p. 444

A Boy in Brazil’s Amazon Sleeps Under an Insecticide-Treated Mosquito Net Fig. 17-7, p. 445

We Can Reduce the Incidence of Infectious Diseases Good news Vaccinations on the rise Oral rehydration therapy Bad news More money needed for medical research in developing countries

Solutions: Infectious Diseases Fig. 17-8, p. 445

What Types of Chemical Hazards Do We Face? There is growing concern about chemicals in the environment that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine system.

Some Chemicals Can Cause Cancers, Mutations, and Birth Defects Toxic chemicals Carcinogens Chemicals, types of radiation, or certain viruses the cause or promote cancer Mutagens Chemicals or radiation that cause mutations or increase their frequency Teratogens Chemicals that cause harm or birth defects to a fetus or embryo

Case Study: PCBs Are Everywhere—A Legacy from the Past Class of chlorine-containing compounds Very stable Nonflammable Break down slowly in the environment Travel long distances in the air Fat soluble Biomagnification Food chains and webs Banned, but found everywhere

Potential Pathways on Which Toxic Chemicals Move Through the Environment Fig. 17-9, p. 447

Some Chemicals May Affect Our Immune and Nervous Systems Some natural and synthetic chemicals in the environment can weaken and harm Immune system Nervous system Neurotoxins: PCBs, arsenic, lead, some pesticides Endocrine system

Science Focus: Mercury’s Toxic Effects Hg: teratogen and potent neurotoxin Once airborne, persistent and not degradable 1/3 from natural sources 2/3 from human activities Enters the food chain: biomagnification How are humans exposed? 1.Inhalation: vaporized Hg or particulates 2.Eating fish with high levels of methylmercury 3.Eating high-fructose corn syrup

Science Focus: Mercury’s Toxic Effects Effects of Hg on humans Damage nervous system, kidneys, lungs Harm fetuses and cause birth defects Who is most at risk? Pregnant women 75% of exposure comes from eating fish

Solutions: Mercury Pollution Fig , p. 449

Some Chemicals Affect the Human Endocrine System Glands that release hormones that regulate bodily systems and control sexual reproduction, growth, development, learning, behavior Hormonally active agents have similar shapes and bind to hormone receptors Gender benders Thyroid disruptors BPA? Phthalates in plastics

Hormones and Hormones Mimics or Blockers Fig , p. 449

How Can We Evaluate and Deal with Chemical Hazards? Scientists use live laboratory animals, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations. Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful chemicals.

Many Factors Determine the Harmful Health Effects of a Chemical Toxicology Toxicity dependent on Dose Age Genetic makeup Multiple chemical sensitivity (MCS) Solubility Persistence Biomagnification

Many Factors Determine the Harmful Health Effects of a Chemical Response Acute effect: immediate or rapid Chronic effect: permanent or long-lasting

Science: Estimating Human Exposure to Chemicals and Measuring Their Effects Fig , p. 452

Case Study: Protecting Children from Toxic Chemicals Analysis of umbilical cord blood: significance Infants and children more susceptible Eat, drink water, and breathe more per unit of body weight than adults Put their fingers in their mouths Less well-developed immune systems and body detoxification processes Fetal exposure may increase risk of autism, asthma, learning disorders

Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity Mice and rats Systems are similar to humans Small, and reproduce rapidly Is extrapolation to humans valid? Dose-response curve: median lethal dose (LD50) Nonthreshold dose-response model Threshold dose-response model

Scientists Use Live Lab Animals and Nonanimal Tests to Estimate Toxicity More humane methods using animals Replace animals with other models Computer simulations Tissue culture and individual animal cells Chicken egg membranes What are the effects of mixtures of potentially toxic chemicals?

Hypothetical Dose-Response Curve Showing Determination of the LD50 Fig , p. 453

Toxicity Ratings and Average Lethal Doses for Humans Table 17-1, p. 453

Science: Two Types of Dose-Response Curves Fig , p. 454

There Are Other Ways to Estimate the Harmful Effects of Chemicals Case reports and epidemiological studies Limitations of epidemiological studies Too few people tested Length of time Can you link the result with the chemical? Cannot be used for new hazards

Are Trace Levels of Toxic Chemicals Harmful? Insufficient data for most chemicals We are all exposed to toxic chemicals Are the dangers increasing or are the tests just more sensitive?

Some Potentially Harmful Chemicals Found in Most Homes Fig , p. 455

Why Do We Know So Little about the Harmful Effects of Chemicals? Severe limitations estimating toxicity levels and risks Only 2% of 100,000 chemicals have been adequately tested 99.5% of chemicals used in the United States are not supervised by government

Pollution Prevention and the Precautionary Principle Those introducing a new chemical or new technology would have to follow new strategies A new product is considered harmful until it can be proved to be safe Existing chemicals and technologies that appear to cause significant harm must be removed 2000: global treaty to ban or phase out the dirty dozen persistent organic pollutants (POPs) 2007 REACH program in the European Union

Individuals Matter: Ray Turner and His Refrigerator 1974: Ozone layer being depleted by chlorofluorocarbons (CFCs) 1992: International agreement to phase out CFCs and other ozone- destroying chemicals Ray Turner: citrus-based solvents to clean circuit boards

How Do We Perceive Risks and How Can We Avoid the Worst of Them? We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices.

The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices Risk analysis Risk assessment Risk management Risk communication Greatest health risks Poverty Gender Lifestyle choices

Global Outlook: Number of Deaths per Year in the World from Various Causes Fig , p. 458

Comparison of Risks People Face in Terms of Shorter Average Life Span Fig , p. 459

Case Study: Death from Smoking Most preventable major cause of suffering and premature death Premature death of 5.4 million per year globally and 442,000 in the United States Could be linked to increased dementia and Alzheimer’s disease Nicotine: additive Effects of passive smoking (secondhand smoke)

Case Study: Death from Smoking How to reduce smoking Taxes Classify and regulate nicotine Bans on smoking in public places Education

Normal Lung and Emphysema Lung Fig , p. 459

Annual Deaths in the U.S. from Tobacco Use and Other Causes Fig , p. 460

Estimating Risks from Technologies Is Not Easy System reliability (%) = Technological reliability (%) x Human reliability (%) To err is human…

Most People Do a Poor Job of Evaluating Risks 1.Fear 2.Degree of control 3.Whether a risk is catastrophic or chronic 4.Optimism bias 5.Want instant gratification without thinking of future harm

Several Principles Can Help Us to Evaluate and Reduce Risk 1.Compare risks 2.Determine how much you are willing to accept 3.Determine the actual risk involved 4.Concentrate on evaluating and carefully making important lifestyle choices

Three Big Ideas 1.We face significant hazards from infectious 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. 2.Because of the difficulty in evaluating the harm caused by exposure to chemicals, many health scientists call for much greater emphasis on pollution prevention.

Three Big Ideas 3.Becoming informed, thinking critically about risks, and making careful choices can reduce the major risks we face.