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

TOXIC BOTTLES?On the trail of chemicals in our everyday lives

CHAPTER 3 INFORMATION LITERACY

TOXIC BOTTLESOn the trail of chemicals in our everyday lives3

Learning 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 toxins


Main 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!


BPA is a synthetic chemical from the 1940s used to line metal food cans and in the production of plastic bottles—including 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 effects

We live in an environment full of toxins3

Synthetic toxins – Many and persistent; don’t degrade over time.Natural toxins – Natural doesn’t always mean safe! Consider arsenic in groundwater.Regulation becomes a challenge – How much is safe?

We live in an environment full of toxins3

Early 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 do—kill pests, including the mosquitoes responsible for malaria. But…

We 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.

Regulation happens even in the face of change3TERMS TO KNOW:Toxins Persistent chemicalsRisk assessmentPrecautionary principle

Risk 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.

Regulation happens even in the face of change3TERMS TO KNOW:Toxins Persistent chemicalsRisk assessmentPrecautionary principle

Risk 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?

Scientific information can generally be divided into two types: primary and secondary3

Primary sources include new and original information from research—usually rigorously reviewed by peers in the scientific community for design, data, and

analysis.


Secondary sources include interpretation of primary sources and lack of peer review. This is what you read in the popular press.


Tertiary sources interpret information from secondary sources, often over-simplifying, while providing additional commentary and stimulating debate over

an issue.

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

TERMS TO KNOW:Information literacy

Primary sourcesPeer review

Secondary sourcesTertiary sources

Case: 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 packaging

Results are in, but does that mean BPA is dangerous in

humans?


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


Evaluating safety How soluble is the substance?Water and other liquids:

May be safer for humans—excrete in urineStill potential toxic at high doses or continual low doseHigh impact on aquatic organisms—easy uptake

Fat-soluble:Cross cell membrane in humans and hard to eliminateSome break down by liverStorage and accumulation in fatty tissue


Bioaccumulation – 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.


TERMS 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.


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 problems

BPA case – Looked at individuals with BPA in urine

and found correlation between BPA concentration and cardiovascular disease.


Toxicology - Determining properties of toxins and their effects on cells and tissuesTesting on animals—in vivo (“in body”)Testing cells in petri dishes—in vitro (“in glass”)

BPA case – Looked at individuals with BPA in urine

and found correlation between BPA concentration and cardiovascular disease.


Testing on animals – in vivo (“in body”)





In vivo and in vitro studies

both show negative effects of BPA—one on

prostate size, the other on cell survival.


Effects of variables on toxicityVariables – Genetics, age, general health status

Lang study – Urine BPA levels of 1455

subjects

Statistical adjustment for specific variables

Diagnosis of seven health conditions compared to BPA

levels


High overlap between high BPA in urine of subjects with and without stroke and liver disease—BPA 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


High overlap between high BPA in urine of subjects with and without stroke and liver disease—BPA 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

Endocrine disruptors cause big problems at small doses3Determining 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.

Endocrine disruptors cause big problems at small doses3

TERMS TO KNOW:Endocrine disruptorsHormoneReceptor

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

Antagonistic effects – Other chemicals reduce or cancel the toxin’s effects.

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



Additive effects – Tther chemicals may increase the effect of the toxin.








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




What does the saying mean? “The dose makes the poison.”

TERMS TO KNOW:Additive effectsAntagonistic effectsSynergistic effects


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 mimic—it binds to estrogen receptors and triggers the effects associated with estrogen:

Feminization of malesLowered sperm countsProduction of egg proteins

Endocrine disrupters don’t 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?



LD50 is lethal dose for 50% of the population



Lower LD50 more toxic

Endocrine disruptors cause big problems at small doses3Determine “safe dose” based on finding threshold dose—dose where effects are first seen—and 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.

Endocrine disruptors cause big problems at small doses3History for another endocrine disrupter: Diethylstilbesterol (DES) used to prevent premature labor—research 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.

Endocrine disruptors cause big problems at small doses3History for another endocrine disrupter: Diethylstilbesterol (DES) used to prevent premature labor—research 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.

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

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

Hormone receptor complex binds to DNA in cell nucleus

How hormones work



Binding activates gene which directs protein production

How hormones work



Binding activates gene which directs protein production

New protein made

Protein changes cellular activity

How hormones workHow hormones work


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.


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

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

TERMS TO KNOW:Critical thinkingLogical fallacies

What about regulation for BPA?










PERSONAL CHOICES THAT HELP3

www.ewg.org/skindeep

UNDERSTANDING THE ISSUE3

UNDERSTANDING THE ISSUE3

ANALYZING THE SCIENCE3

EVALUATING NEW INFORMATION3

www.ewg.org/skindeep

http://www.ewg.org/skindeep

MAKING CONNECTIONS3

www.ama-assn.org/resources/doc/csaph/csaa-00.pdf

http://www.ama-assn.org/resources/doc/csaph/csaa-00.pdf

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