Midterm Flashcards
Number of chemicals in commerce?
85k-250k
Unclear true number since not all are admitted
What is an HPV?
High production volume chemicals
What is the number of HPVs?
3,000
How much HPV (percentage wise) have basic risk information? And what is the number of basic screening tests?
7%
43% are missing every test
57% have at least one test
There are 6 basic screening tests (called SIDs: screening information dataset)
How many people have water stress (pollutants) in their local rivers?
~ 5,000 mill
What are NAQs?
National air quality standards
How many Americans live in areas that exceed NAQs?
1/3rd
How many liters of air does a person inhale every day?
~11,000
How many people die every year due to pollution?
~9 mill
What is the GBD and how does pollution affect it?
Global burden of disease
Inc. due to pollution
What does the Lancet Commission (science reports) say about pollution?
Inc. GBD (connect multiple exposures to health effects)
It is not being dealt with
Vulnerable groups are disproportionately impacted
There are win-win solutions
Advocates usually skip over the necessary processes
What is the dilution paradigm?
Solution to pollution is dilution
It was a widespread belief
Ex. factories made tall stacks so smoke would be sent up and disperse in air (created acid rain)
What is the boomerang paradigm?
What is thrown away can come back and hurt you
Precautionary steps should be taken to stop any unknown longterm effects
Ex. Love canal
What is DDT?
Dichlorodiphenyltrichloroethane
Used in 1940s+ as first modern pesticide (opens sodium channels in insect neurons; caused hyperstimulation)
Problems with DDT?
Doesn’t break down
Soluble: can pass through membranes b/c it looks like cholesterol-based hormone
T1/2 is 2-15 years
Accumulates in fatty tissues
Metabolizes to DDE in liver (a reactive metabolite that is more toxic and impairs reproductive enzymes and reduces calcium)
DDT + congeners induce CYTP450 (oxidative stress)
Biomagnifies 10 mill-fold (trophic birds are high risk)
Benefits of DDT?
Used in WWII: the first war more people died from trauma than disease
Against malaria: dec from 1 mill cases to 9 in Taiwan over 24 years
What is biomagnification?
The increase of chemical concentrations through the foodchain
What is bioaccumulation?
The accumulation of a chemical concentration in ONE individual over their lifespan
From ALL external sources and ALL internal processes
What is the importance of “Silent Spring”?
Realization that humans alter the ecosystem and have long-term consequences through “invisible” technology
- Look at DDT, Agent Orange,, and Love Canal
Caused a policy change through a congressional hearing initiated by Kennedy
What does the general population use that affect pollution?
Disposing meds (most are tossed or flushed: 89.4%)
Organic wastewater contaminants (common are coprostanol, cholesterol, and caffeine)
PPCPs (pharmaceuticals & personal care products)
Endocrine disruptors (ex. artificial hormones) (highest concentration was detergent metabolites, then steroids and plasticizers)
Antibiotics
*These all are ‘pseudo’-persistent
What is ‘pseudo’-persistence?
chemicals that might break down easily, but are used on a daily basis so never leave the environment
What is a contaminant?
A substance that is present in greater than natural concentrations as a result of human activity
What is ecotoxicology?
(ecology + toxicology)
Definitions change over time; but are generally the same:
- Toxicology branch concerned with study of toxic effects, caused by natural & synthetic pollutants, to the constituents of the ecosystem (animals, vegetable, microbial)
- The study of poisons on individual organisms, to the ecological effects of pollutants
What is a pollutant?
A substance that occurs in the environment at least in part of human activity and which has a deleterious effect on living organisms
What is xenobiotic?
A foreign chemical not produced in nature and not considered a constitutive component of a biological system
What are the SCALES of an interdisciplinary field?
Molecules to ecosystems
Complexity of hierarchical scales
Learning adverse outcome pathways (toxicant to population response)
What are the SPECIALTIES of an interdisciplinary field?
Complexities of different specialities (different fields working together to determine outcomes)
List the organic legacy pollutants…
PAHs (Polycyclic aromatic hydrocarbons)
PCBs (polychlorinated biphenyls)
POP (Persistent organic pollutants) “dirty dozen”
Organophosphate insecticides
What are organic pollutants?
Contain carbon and at least 1 C-H covalent bond
Behavior dependent on the structure
Source is natural or anthropogenic
What are the characteristics of the C-H covalent bond?
Low polarity
Low water solubility
What are the basic characteristics of PAHs?
2+ fused benzene rings
Persistent (years -> decades)
Natural and anthropogenic (most common)
Have pyrolysis reactions (decomposes at high temps w/out O2)
Examples of natural sources of PAHs…
Volcanos
Fires
Natural oil seep
Examples of anthropogenic sources of PAHs…
Industry generators
Internal combustion engines
Grills
Offshore oil platforms
What happens to PAHs as their molecular weight increases?
Dec. volatilization Inc. bioaccumulation Inc. absorption to particles Dec. solubility (inc. Kow) Inc. environmental persistence
What happens to PAHs released on land?
Evaporate
Penetrate soil -> metabolized by plants/soil invertebrates
What happens to PAHs released in water?
Evaporate
Float
Degradation by microbes
Metabolized by algae/zooplankton/fish…
How do PAHs affect thermoregulation of birds?
?
What are the ecotoxicological effects of PAHs?
Physical: smothering, reduced light
Habitat change: alter pH, dec. O2, dec. food availability
Toxicity: cellular membranes and enzyme-bound membranes
What are the properties of PCBs?
Low water solubility (high in solvents & fats) Low vapor pressure High dielectric constant High flashpoint High thermal conductivity Inert
What are the industrial uses of PCBs?
Used in transformers and capacitors
A coolant, lubricant, PVC in electrical wires, caulking sealant, and wood floor polish
How are PCBs different from PAHs?
PCBs are chlorinated
- It adds a charge to the chemical
How does chlorine affect PCBs?
More chlorine = more oily
Percentage of chlorine changes the properties
What happens to PCBs in the environment?
Persistent: resist breakdown (can take a century) and cycle between air, water, & soil
Transportable: absorb to particles so carried long distances (lighter compounds move further)
Accumulate: move up food chains in fatty tissues (a PBT)
What is a PBT?
A Persistent Bioaccumulant Toxin
List the characteristics of POPs…
Persist in environment
Bioaccumulate through food web
Pose risk of causing adverse effects to human health & environment
What happened to the “dirty dozen”?
They were banned
12 POPs that were deemed unsafe
Ex. DDT
What are organophosphate insecticides?
Initially developed as nerve gas agents
Inhibit acetylcholinesterase activity -> blocks acetylcholine metabolism
- Causes muscular rigidity & paralysis in insects
High water solubility
Low soil persistence
T1/2 = days to week (however, consistent use)
Why are metals ubiquitous (everywhere)?
Because they are used in countless industries, commercial and consumer products
* They are the most common ubiquitous chemicals
What is a unique property of metals?
They are elemental: they do NOT breakdown
How would you treat acute metal toxicity?
Using chelators (compounds that form complexes with metal ions) Useless with chronic toxicity
What is a problem with chelators?
Can bind to the wrong thing: there are many useful metals in the body that might be taken instead
What are toxic mechanisms of metals?
Promoter of oxidation
Competition for divalent cation binding sites
Binding of sulfhydryl groups
What are the sources of arsenic?
Industrial: from use in wood preservation & in microelectronics industry
Human environment: from fallout of smelters and arsenic pesticide spraying
Natural: Deep-water well water ingestion
What are key exposure routes of pollutants?
Ingestion
Inhalation
Dermal contact
What is the percentage of natural mercury sources? What are they from?
30-40%
Soil, ocean, geogenic, evapotranspiration, recycling
What is mercury most used for?
Small-scale gold mining (30%) Chlor-Alkali (21%) Batteries (18%) Dental amalgam: cavity caps (8%) Catalyst for vinyl chloride monomer... (8%)
What is the cycle of mercury from coal burning to the environment?
Hg-S in coal ->
releases Hg^0 as vapor when burned -> lasts up to a year in atmosphere as Hg^0 ->
oxidizes to Hg^2+ ->
drops to ground ->
converts to MeHg via sulfate reducing bacteria (SRB) ->
Biomagnifies
What does methylmercury do to the body (MeHg)?
A neurodevelopment threat (especially in pregnant women)
- Crosses membranes (including blood brain barrier & placenta)
- High affinity for protein thiols (multiple targets)
Bioaccumulates in muscles
What is the movement of the neurotoxicity of MeHg due to continued exposure?
Molecular & neurochemical disruption ->
Sub-clinical neurophysiological impacts -> overt neurotoxicity & clinical “Minimata” disease
What is the “Minimata” disease?
Minimata was the name of a Japanese town exposed to chemicals from a plant
Caused disease form MeHg
What is a point source?
Any single identifiable source of pollution from which pollutants are discharged
What is the NPRI?
National pollutant release inventory
Canada’s inventory of pollutant releases, disposals, and transfers
Has over 320 pollutants from over 7,000 facilities
What is a non-point source?
Pollutants from diffuse sources
This is mainly due to precipitation
How does the polarity affect pollutants?
Determines if they are water soluble
More negative = more water soluble
What is the Kow?
Concentration in octanol/concentration in water
What happens if there is a high Kow?
Hydrophobic (water-resistant)
Lipophilic (fat-soluble)
What happens if there is a low Kow?
Hydrophilic (water-soluble)
Lipophobic (fat-resistant)
When does the vapor pressure decrease?
With inc. weight
What is fugacity?
The combination of the polarity, Kow, and vapor pressure to determine:
- escaping tendency from compartment
- establish equilibrium in chemicals between environmental phases
What is the biota?
Air, soil, and water
What is exposure?
Any condition which provides an opportunity for an external environment agent to contact human body
Magnitude x frequency x duration
What is exposure assessment?
Measure or estimate the intensity, frequency, or duration of human exposure to an agent
Dose-response assessment?
Characterize relationship between varying exposures and incidences of adverse effects in exposed populations
What is PPM?
part per million
What is PPB?
part per billion
Bioconcentration is…
Net accumulation of a contaminant in an organisms from water ONLY
What are the key components of bioaccumulation?
Uptake
Biotransform
Eliminate
What is biotransformation?
Biologically mediated transformation of a chemical compound to another
Involves enzymes
Leads to inc. elimination
How does biotransformation occur in metals?
Organic conversion by microbes
Sequestration by metallothioneins
Biomineralization
How does biotransformation occur in organic chemicals?
Add polarity to more easily leave body (water soluble)
Conjugate polar chemicals
What are the types of elimination of chemicals from the body?
Excretion: physical process
Biotransformation: chemical process
Depuration: contaminated organism placed in clean environment (loss of contaminant over time)
How does the liver help with excretion?
Deals with organics mostly
Deals with large compounds
How does the kidney help with excretion?
Deals with metals mostly
Deals with smaller compounds
What is toxicology?
Study of adverse effects of chemicals on living organisms
What is a dose response curve?
Describes how response to a toxicant changes with the dose
Supports causality between exposure and effect
What are the assumptions of the dose response curve?
Response is due to the chemical
Magnitude of response due to the dose
Quantifiable method used to assess response
What are biomarkers?
- Biological response to a chemical that gives a measure of exposure & toxic effect
- Alterations in cellular or biochemical components, or processes, structure, or functions that is measurable in a biological system or sample
What biomarkers are used to study PAHs
DNA adducts (chemical covalently binds to DNA)
COMET assay
Phase 1 or 2 biomarkers
CYP1a/EROD
Genotoxicity is…
When chemicals effect DNA
Cause DNA adducts
What does a Comet assay do?
Measures DNA strand breaks in cells
What are oxidative stress biomarkers?
Enzymes turned on when chemicals are polarized. There are reactive byproducts that attack DNA or oxidize lipids
What does CYP1a do?
Chemical binds in cell that is taken to nucleus. Enzymes are turned on to attack chemical
CYP1a is a marker via EROD Assay to test if chemical is in nucleus.
What do scientists care most about with pollution?
Growth
Reproduction
Survival
What are endocrine disrupting chemicals (EDCs)?
Exogenous substance or mixture that alter functions of the endocrine system and consequently cause adverse health effects in an intact organisms, its progeny, or the population
What can EDCs do to cells?
Mimic natural hormones by binding to their receptors
Alter recognition, biosynthesis, storage, release, transport, and clearance of hormones
What do EDCs do to the body?
Decline sperm quality Impari fertility Inc. spontaneous abortions Decline sex ratios (less men) Endometriosis Early puberty Neurobehavioral disorders Pop. decline
What is the endocrine system?
Collection of ductless tubes
Synthesize and secrete hormones
How much EDCs are needed to cause effects?
About ppb
Why would whole lakes be used as experiments?
Need ecosystems to show compelling evidence of changes in the environment due to pollution (such as acid rain, mercury, eutrophication…)
Biggest: 58 pristine lakes set aside in 1968 (was shut down for a time due to budget, but reopened by scientists as a non-profit)
What is tiered testing?
Level 1: sorting & prioritization based upon existing info
Level 2: In vitro assays providing mechanistic data
Level 3: In vivo assay providing data about single endocrine mechanisms and effects
Level 4: in vivo assay providing data about multiple endocrine mechanisms and effects
Level 5: in vivo assays providing data on effects from endocrine and other mechanisms
What is the adverse outcome pathway?
Showing step by step (concept model) the toxicant from making to outcomes
What is the general adaptation syndrome (GAS)?
Non-specific changes constituting the body’s attempt to reestablish or maintain homeostasis while under the influence of a stressor. Hormones are released to get body to fight, but deplete after time.
Ex. getting sick when continually stressed
What does the GAS have to do with pollutants?
The cortisol stress response can be impaired due to chemicals such as PAHs, PCBs, mercury, etc.
Can’t mount response b/c hormones deplete over time
What is behavioral ecotoxicology?
Interaction of organisms with its external environment
What are challenges of behavioral ecotoxicology?
Latency period
Inter species sensitivity
Are behavioral changes due to ecology or toxicology?
Not easy to monitor in nature
Is there any tolerance, resistance, or adaptation?
What is commonly measured in behavioral ecotoxicology?
Avoidance (change in response to stimulus)
Activity level
Feeding
Performance
