CHAPTER 2 SCIENCE LITERACY AND THE PROCESS OF SCIENCE SCIENCE AND THE SKY Solving the mystery of disappearing ozone

TOXIC BOTTLES?On the trail of chemicals in our everyday livesCHAPTER 3 INFORMATION LITERACY

1TOXIC BOTTLESOn the trail of chemicals in our everyday lives3Learning Outcomes

At the end of this chapter, you should know:

The importance of information literacy and ways logic can be distorted

How to evaluate the quality of information

How risk assessment helps determine safe exposure levels to environmental toxins2TOXIC BOTTLESOn the trail of chemicals in our everyday lives3Main Concept

Information contributing to our knowledge about nature is being continually revised as we learn more about toxins and biochemical processes.

Not all sources of information are equally valid or trustworthy!

3TOXIC BOTTLESOn the trail of chemicals in our everyday lives3

BPA is a synthetic chemical from the 1940s used to line metal food cans and in the production of plastic bottlesincluding baby bottles.

Studies began showing an association between BPA and serious medical conditions.

BPA wasbanned in Canada and the U.K.

Plastics industry challenged the science claiming BPA was safe.

Without government protection, what should we do?

Case: Bisphenol A (BPA) and health effects4We live in an environment full of toxins3Synthetic toxins Many and persistent; dont degrade over time.Natural toxins Natural doesnt always mean safe! Consider arsenic in groundwater.Regulation becomes a challenge How much is safe?

5We live in an environment full of toxins3Early insight came from Rachel Carson in her 1962 book Silent Spring, in which she highlighted a significant die-off following only two decades of extensive use of DDT and other herbicides and pesticides.DDT was doing what it supposed to dokill pests, including the mosquitoes responsible for malaria. But

6We live in an environment full of toxins3Carson identified three specific concerns that had not yet been addressed:Some chemicals have large effects in small doses.

Certain stages of human development are especially vulnerable to effects.

Mixtures of different chemicals can have unexpected impacts.

One result of the book was a movement toward stricter regulations for chemical pesticides and a U.S. ban on DDT.

7Regulation happens even in the face of change3TERMS TO KNOW:Toxins Persistent chemicalsRisk assessmentPrecautionary principleRisk Assessment

The goal of risk assessment is to weigh the costs and benefits associated with any specific chemical.

In reality, it is impossible to fully understand and assess all potential interactions among the many chemicals to which we are exposed on a daily basis.

Reality includes practicality, economic forces, and the basic need for the chemical.

8Regulation happens even in the face of change3TERMS TO KNOW:Toxins Persistent chemicalsRisk assessmentPrecautionary principleRisk AssessmentFood and Drug Administration (FDA) Authority that regulates and bans harmful chemicals

In uncertainty, better safe than sorry, known as the precautionary principle until exposure limits are determined, versus Innocent until proven guilty, using recalls rather than prevention. This leaves the burden of proof on the public.

How do we weigh information from which we make our decisions?

9Scientific information can generally be divided into two types: primary and secondary3Primary sources include new and original information from researchusually rigorously reviewed by peers in the scientific community for design, data, and analysis.

10Scientific information can generally be divided into two types: primary and secondary3Secondary sources include interpretation of primary sources and lack of peer review. This is what you read in the popular press.

11Scientific information can generally be divided into two types: primary and secondary3Tertiary sources interpret information from secondary sources, often over-simplifying, while providing additional commentary and stimulating debate over an issue.

12What are dangers presented by toxins and how do we determine safe exposure levels?3TERMS TO KNOW:Information literacyPrimary sourcesPeer reviewSecondary sourcesTertiary sourcesCase: Bisphenol A (BPA) and health effectsSampling: 2000 urine samples90% positive for BPA

Average concentration 2.6 ppbTop 5% almost 16 ppb Beyond the amount found to cause harm in rodents

Concentration decreasing with age indicates BPA leaching from food containers into bodies.

Greater exposure among younger people as more products used BPA in packagingResults are in, but does that mean BPA is dangerous in humans?

13What are dangers presented by toxins and how do we determine safe exposure levels?3

Evaluating safety How persistent is the substance?

Low persistence - Break down quickly with sunlight

High persistence - Long time to break down and potential environmental impact long after initial release

14What are dangers presented by toxins and how do we determine safe exposure levels?3

Evaluating safety How soluble is the substance?Water and other liquids:May be safer for humansexcrete in urine

Still potential toxic at high doses or continual low dose

High impact on aquatic organismseasy uptake

Fat-soluble:Cross cell membrane in humans and hard to eliminate

Some break down by liver

Storage and accumulation in fatty tissue

15What are dangers presented by toxins and how do we determine safe exposure levels?3Bioaccumulation Fat-soluble substances build up in tissues of an organism over time.Biomagnification Higher on the food chain and able to consume the entire lifetime of toxins in their preyTuna and swordfish are large predators high on the ocean food chain. They accumulate and magnify mercury, PCBs, and DDT.

16What are dangers presented by toxins and how do we determine safe exposure levels?3TERMS TO KNOW:BioaccumulationBiomagnificationEpidemiologistToxicologistsIn vitro studyIn vivo studyPersistenceSolubility

Biomagnification Higher on the food chain and able to consume the entire lifetime of toxins in their prey

Tuna and wwordfish are large predators high on the ocean food chain. They accumulate and magnify mercury, PCBs, and DDT.

17

What are dangers presented by toxins and how do we determine safe exposure levels?3

Epidemiologists - Determining cause and effectLook for health problem in a specific population and work backwards for cause or look at group with exposure and identify common health problemsBPA case Looked at individuals with BPA in urine and found correlation between BPA concentration and cardiovascular disease.

18

What are dangers presented by toxins and how do we determine safe exposure levels?3

Toxicology - Determining properties of toxins and their effects on cells and tissuesTesting on animalsin vivo (in body)Testing cells in petri dishesin vitro (in glass)BPA case Looked at individuals with BPA in urine and found correlation between BPA concentration and cardiovascular disease.

19

What are dangers presented by toxins and how do we determine safe exposure levels?3

Testing on animals in vivo (in body)

20

What are dangers presented by toxins and how do we determine safe exposure levels?3

21

What are dangers presented by toxins and how do we determine safe exposure levels?3

22

What are dangers presented by toxins and how do we determine safe exposure levels?3

23

What are dangers presented by toxins and how do we determine safe exposure levels?3

In vivo and in vitro studies both show negative effects of BPAone on prostate size, the other on cell survival.

24

What are dangers presented by toxins and how do we determine safe exposure levels?3Effects of variables on toxicityVariables Genetics, age, general health statusLang study Urine BPA levels of 1455 subjects

Statistical adjustment for specific variables

Diagnosis of seven health conditions compared to BPA levels

25What are dangers presented by toxins and how do we determine safe exposure levels?3High overlap between high BPA in urine of subjects with and without stroke and liver diseaseBPA not implicated

Those with higher BPA levels showed significantly higher incidence of diabetes and CVD.

Almost no overlap between those with and without diabetes and CVD beyond BPA ppb 4-5

26What are dangers presented by toxins and how do we determine safe exposure levels?3High overlap between high BPA in urine of subjects with and without stroke and liver diseaseBPA not implicated

Those with higher BPA levels showed significantly higher incidence of diabetes and CVD.

Almost no overlap between those with and without diabetes and CVD beyond BPA ppb 4-5

27Endocrine disruptors cause big problems at small doses3

Determining toxicityEffects of variables on toxicityVariables Genetics, age, general health status

Individual factors Some toxins are more of a problem in the very young or the very old, or those who are ill.

Genetic factors may make a person more or less vulnerable to the toxin.

Exposure Whether the toxin is inhaled, ingested, or contacts the skin makes a difference in toxicity.

Frequency of exposure also matters.28Endocrine disruptors cause big problems at small doses3TERMS TO KNOW:Endocrine disruptorsHormoneReceptorAdditive effects Other chemicals may increase the effect of the toxin.

Antagonistic effects Other chemicals reduce or cancel the toxins effects.

Synergistic effects Chemicals increase the effects of the toxin, even beyond expectations.

29Endocrine disruptors cause big problems at small doses3TERMS TO KNOW:Endocrine disruptorsHormoneReceptorAdditive effects Tther chemicals may increase the effect of the toxin.

Antagonistic effects Other chemicals reduce or cancel the toxins effects.

Synergistic effects Chemicals increase the effects of the toxin, even beyond expectations.

30Endocrine disruptors cause big problems at small doses3TERMS TO KNOW:Endocrine disruptorsHormoneReceptorAdditive effects Other chemicals may increase the effect of the toxin.

Antagonistic effects Other chemicals reduce or cancel the toxins effects.

Synergistic effects Chemicals increase the effects of the toxin, even beyond expectations.

31Endocrine disruptors cause big problems at small doses3Determining toxicityEffects of variables on toxicityVariables Genetics, age, general health status

Additive effects Other chemicals may increase the effect of the toxin.

Antagonistic effects Other chemicals reduce or cancel the toxins effects.

Synergistic effects Chemicals increase the effects of the toxin, even beyond expectations.What does the saying mean? The dose makes the poison.

TERMS TO KNOW:Additive effectsAntagonistic effectsSynergistic effects32Endocrine disruptors cause big problems at small doses3

TERMS TO KNOW:Dosed-response curveLD50 (lethal dose 50%)Endocrine disrupters interfere with the endocrine system.They mimic a hormone or prevent a hormone from having an effect.BPA is an estrogen mimicit binds to estrogen receptors and triggers the effects associated with estrogen:Feminization of malesLowered sperm countsProduction of egg proteins Endocrine disrupters dont follow the dose makes the poison.The can have one set of effects at a low dose and no effect or different effects at higher doses.

How can we determine the effect of a dose?33Endocrine disruptors cause big problems at small doses3TERMS TO KNOW:Dosed-response curveLD50 (lethal dose 50%)

LD50 is lethal dose for 50% of the population34Endocrine disruptors cause big problems at small doses3TERMS TO KNOW:Dosed-response curveLD50 (lethal dose 50%)

Lower LD50 more toxic35Endocrine disruptors cause big problems at small doses3

Determine safe dose based on finding threshold dosedose where effects are first seenand continue testing effects at higher doses or starting at high doses and reducing dosage until no effects are seen.

For endocrine disruptors, high- and low-dose effects must be assessed separately.

36

Endocrine disruptors cause big problems at small doses3History for another endocrine disrupter: Diethylstilbesterol (DES) used to prevent premature laborresearch indicated an exact response for humans and for a strain of rat. Using this same strain of rat, BPA showed increased postnatal growth, early onset of sexual maturation in females, decreased testosterone and increased prostrate size, altered immune function, and increased embryo mortality.

37

Endocrine disruptors cause big problems at small doses3History for another endocrine disrupter: Diethylstilbesterol (DES) used to prevent premature laborresearch indicated an exact response for humans and for a strain of rat .Using this same strain of rat, BPA showed increased postnatal growth, early onset of sexual maturation in females, decreased testosterone and increased prostrate size, altered immune function, and increased embryo mortality.

38Endocrine disruptors cause big problems at small doses3How hormones workSteroid hormone enters cells and binds to receptor

39Endocrine disruptors cause big problems at small doses3Steroid hormone enters cells and binds to receptor

Hormone receptor complex binds to DNA in cell nucleusHow hormones work

40Endocrine disruptors cause big problems at small doses3Steroid hormone enters cells and binds to receptor

Hormone receptor complex binds to DNA in cell nucleus

Binding activates gene which directs protein productionHow hormones work

41Endocrine disruptors cause big problems at small doses3Steroid hormone enters cells and binds to receptor

Hormone receptor complex binds to DNA in cell nucleus

Binding activates gene which directs protein production

New protein made

Protein changes cellular activity

How hormones workHow hormones work

42Endocrine disruptors cause big problems at small doses3

Based on effect of low-dose BPA on rodents, and the history of endocrine disruptors like DES, what might be the potential risks to pregnant mothers, developing fetuses, and young children?

BPA broken down in mother and excreted in urine? NO

Protection of fetus by placenta? NO

BPA in both maternal and fetal blood at levels high enough to cause harm.43Endocrine disruptors cause big problems at small doses3

Based on effect of low dose BPA on rodents, and the history of endocrine disruptors like DES, what might be the potential risks to pregnant mothers, developing fetuses, and young children?

BPA broken down in mother and excreted in urine? NO

Protection of fetus by placenta? NO

BPA in both maternal and fetal blood at levels high enough to cause harm

44

Critical thinking skills give us the tools to uncover logical fallacies in arguments or claims3

TERMS TO KNOW:Critical thinkingLogical fallaciesWhat about regulation for BPA?45

Critical thinking skills give us the tools to uncover logical fallacies in arguments or claims3

TERMS TO KNOW:Critical thinkingLogical fallaciesWhat about regulation for BPA?

46

Critical thinking skills give us the tools to uncover logical fallacies in arguments or claims3

TERMS TO KNOW:Critical thinkingLogical fallaciesWhat about regulation for BPA?

47

Critical thinking skills give us the tools to uncover logical fallacies in arguments or claims3

TERMS TO KNOW:Critical thinkingLogical fallaciesWhat about regulation for BPA?

48

PERSONAL CHOICES THAT HELP3

www.ewg.org/skindeep

49UNDERSTANDING THE ISSUE3

50UNDERSTANDING THE ISSUE3

51ANALYZING THE SCIENCE3

52EVALUATING NEW INFORMATION3www.ewg.org/skindeep

53MAKING CONNECTIONS3www.ama-assn.org/resources/doc/csaph/csaa-00.pdf

54