Midterm part 1/first half (Q1-15)

Question 1

1. Be able to provide examples of potential ethical challenges faced by environmental health professionals, and how they might be avoided/resolved.

Answer 1

• Finding the distinction between right and wrong. Weight the cost/benefit of the action(s) on the environment
• Difference between advocacy and activism-supporting change for the between without going to the extreme of distorting the truth or letting the ends justify the means.
• Not forging to distorting info to further some agenda
• Recognizing that we all have a personal stake in the way things “come out” but we need to be objective in our analysis and ethical. Recognize that you are in a position of trust/authority.
• Example: your job is to review a nuclear use application but your personal opinion is anti-nuclear…need to be objective when assessing the issue and not allow your personal feelings cloud objectivity.

Question 2

2. Be able to describe how “systems thinking” (identification of personal, scientific, regulatory/institutional and cultural factors) can be used to assist in the analysis and resolution of environmental health problems.

Answer 2

• The “Systems Approach” to environmental health practice is integral in problem identification for risk assessment or risk management.
• It emphasizes the identification of four levels associated with environmental risk management.
o Technical/scientific factors (can contribute research/evidence based solutions)
o Institutional/regulatory factors (needed for laws/regulations)
o Sociocultural factors (cultural aspects to consider for specific populations, the “cultural collective”
o Individual/personal factors (personal collective)
• Consider all of these factors in developing an informed professional ethic.
• The precautionary principle plays a large part
o Preventive, anticipatory measures should be taken when an activity raises threats of harm to the environment, wildlife, or human health, even of some cause and effect relationships are not fully established.
• Many environmental problems have multiple dimensions to them (scientific, personal, regulatory/institutional, and sociocultural factors)
o Scientific and institutional are the objective side
o Personal and cultural are the subjective side

Question 3

3. Know the goals and general approach to each of the following environmental regulations:a. Clean Air Act

Answer 3

: A comprehensive federal law that regulates (EPA) air emission from stationary and mobile sources.
• Goal: To keep the ambient air quality from becoming more polluted
• Approach:
o Set standards for ambient air quality and a threshold level that apply to ambient air and permits specify emission limits and pollution control equipment.
o Primary standards protect against the health impact
o Secondary standards protect trees, livestock, buildings, etc.
o NAAQS: National Ambient Air Quality Standards-requires permits, specifies emission limits
o MACT: Maximum achievable control technology standards-best of the best pollution control equipment
o Designed “attainment areas” where ambient air quality was acceptable and “non-attainment areas” where air was polluted and regulated more strictly to prevent further pollution
o Regulated factor release of pollution “at the stack”
 Required contracts/permits with EPA that apply until factory is updated/renovated
 After renovation, the factory must have “maximum available control technology” to get a new permit

Question 4

3. Know the goals and general approach to each of the following environmental regulations: b. Clean Water Act:

Answer 4

b. Clean Water Act: the primary federal law in the United States governing water pollution
o Goal: to restore and maintain the chemical, physical, and biological integrity of the nation’s waters
o Approach:
o Set a lot of standards
 Ambient water quality standards
• Based on what concentration of pollutant would not hurt the most sensitive species X a “safety factor”
 Discharge standards for industry
• How much and what concentration of pollutant can be discharged per day
 Categorical standards/industrial regulations
• Technology based-defined by how well treatment and control technologies are working and are different/specific for each kind of industry
 Pre-treatment standards
• Have to be met for water from factory going to a POTW (publicly owned treatment works)
o Required national pollutant discharge elimination system (NPDES) Permits
 For any point source facility with wastewater discharge
 Including POTWs
 Best available technology
o Provided funding for POTW
 Initial $$ to build treatment plants
 $$ for upgrades

Question 5

3. Know the goals and general approach to each of the following environmental regulations: c. Safe Drinking Water Act:

Answer 5

c. Safe Drinking Water Act:
o Goal: To ensure the purity of drinking water from public water systems
o Approach:
o Set drinking water purity standards
 Based on health effects on humans
 Regulates at the point of distribution, not at the tap
 MCL (max contaminant level) is enforced
• MCLgoal is “ideal” but not realistic or enforced
o Protect water sources
 Especially sole source aquifers (main drinking source for a community)
 Regulates underground waste injection
• Except for energy industry (hydrofracking)
o Create system to notify the public of unsafe water

Question 6

3. Know the goals and general approach to each of the following environmental regulations: d. Toxic Substance Control Act:

Answer 6

d. Toxic Substance Control Act:
o Goal: Prevents the introduction of hazardous chemical products into commerce and applies to NEW chemical products.
o Approach:
o Inventory and assess all existing chemicals that are being used in commerce
 TRECS (Registry of Toxic Effects of Chemical Substances) has 160,000 chemicals
 Features GRAS (grandfathered existing chemicals) 62,000 chemicals that were automatically assumed to be of an “unreasonable risk”
o Assessed all new chemicals via the pre-manufacture notice (PMNA)
 Manufacturer has to give EPA basic environmental behavior and toxicity info
 EPA reviews and approves/bans chemical use or can ask for further testing
 Decision is based on intended use of produced and the manufacturer must notify the EPA if a significant new use is proposed
 To ban a chemical, the EPA must show
• Unreasonable risk
• Cost-benefit analysis
• Least burdensome regulation

Question 7

3. Know the goals and general approach to each of the following environmental regulations:e. Resource Conservation and Recovery Act:

Answer 7

e. Resource Conservation and Recovery Act: (RCRA) is a “cradle to grave” management of hazardous waste, where the generator of this waste must notify the EPA and specific handling, labeling, storage, and disposal requirements are enforced.
o Goal: Ensure safe disposal of solid waste
o General Approach
o Created solid waste landfills for solid, sanitary, and residential waste
o Set regulations for “cradle-to-grave” handling of hazardous waste
 Characteristics that make waste automatically hazardous:
• Flammable, corrosive, reactive, 10x MCL
 Includes a time frame for handling, storage, transport, treatment, and final disposal
 Waste manifest for transporters so that EPA can keep track
 Requirements for disposal facilities and underground storage tanks for storing petroleum or other hazardous substances

Question 8

3. Know the goals and general approach to each of the following environmental regulations: f. Comprehensive Environmental Response, Compensation and Liability Act

Answer 8

f. Comprehensive Environmental Response, Compensation and Liability Act: (CERCLA) addresses the cleanup of uncontrolled release of hazardous substances into the environment.
o Goal: to clean up a hazardous area where waste has been disposed of improperly, but the person(s) responsible is not obvious or easily determined.
o “Clean up now, the responsible party pays later”
o Approach:
o Establish a superfund using taxes on oil and other chemicals to pay for cleanup
o Established idea of “strict, joint, and several liability”
 Strict liability- no excuses, polluted area has to be cleaed up
 Joint liability- all involved parties are jointly responsible
 Several liability- EPA can “sever” the responsibility by choosing which of the jointly liable parties has to pay for it, or tell them to figure it out themselves (sue each other, etc.)

Question 9

5. Understand the definition of and how the following properties effect chemical fate and transport:
   a. Water solubility

Answer 9

a. Water solubility: the factor controlling the ability of a solid to dissolve in water and is controlled by the polarity of the molecule.
o A factor that has the most bearing on the movement of molecules in water. If compounds dissolve in water, it can “move” with the water, think of water moving through soil and if a toxic substance has high water solubility, it can dissolve in water and move with it towards the water table/source.
o Ksp is the solubility product, the higher the Ksp, the more water soluble a molecule is and therefore the more concern a toxic substance may become.
o Also plays a role in lake turnover where O2 levels can influence how water-soluble some inorganic molecules are. Inorganic compounds have a Ksp and solubilize in ionized form only, organic compounds generally do not ionize.
o Order of solubility: alcohols (almost infinitely soluble), aldehydes, organic acids, ketones, aliphatic, aromatics, chlorinated compounds (the more Cl-, the less soluble).
o If something is water soluble, it will get into the water moving through the soil, the more water soluble, the less it will get hung up on particles that more it will dissolve into groundwater (adsorption is the property of a chemical to adhere to soil particles-see below).

Question 10

5. Understand the definition of and how the following properties effect chemical fate and transport: b. kOW-Octanol/Water Partition Coefficient: :

Answer 10

b. kOW-Octanol/Water Partition Coefficient: useful in prediction the mobility and accumulation of organic compounds
o A high Kow indicates a high potential to accumulate or become absorbed by organic materials in soil or tissue.
o It approximates potential for bioaccumulation in fish and animal tissue.
o Compounds that are water soluble like to be in water, where non-soluble compounds like to be in non-polar environments such as adipose tissue. The more water-soluble (high Ksp) the less bio-accumulative.
o The equation: Kow=Co/Cw, where Co= concentration of chemical in octanol phase and Cw is the concentration of chemical in aqueous phase.

Question 11

5. Understand the definition of and how the following properties effect chemical fate and transport: c. Soil Adsorption

Answer 11

c. Soil Adsorption: the extent to which an organic chemical partitions itself between solid and solution phase of saturated soil, runoff, and sediment.
o It controls accumulation in sediment and leaching into groundwater.
o Low water solubility and high carbon content favors soil/sediment adsorption.

Question 12

5. Understand the definition of and how the following properties effect chemical fate and transport: d. Soil Adsorption Coefficient kOC

Answer 12

d. Soil Adsorption Coefficient kOC = ug adsorbed/g organic carbon divided by ug/ml solution.
o A highly water-soluble compound has a low Koc value.
o A high organic carbon content soil or high surface area (fine particle size) soil will adsorb more compound
o If a compound adsorbs to soil, it can enter the sediment of the lake through runoff, but if it is more dissolved in the water (higher water solubility), it will have a higher chance of being biodegraded because it is easier for microbial enzymes to break chemical bonds in the vicinity of polar areas, such as those occupied by OH groups. It is also easier for a polar/water soluble compound to become dissolved (will be established at a higher concentration) in the polar environment occupied by microorganisms, so more material is effectively available for degradation.

Question 13

5. Understand the definition of and how the following properties effect chemical fate and transport: e. Vapor pressure:

Answer 13

e. Vapor pressure: equilibrium between vapor and liquid forms of an organic compound,
o It is a pressure that is exerted by the vapor onto the liquid.
o The higher the VP of the liquid, the more volatile it is and the greater the ability to enter the air (evaporate).
o Low VP will not volatilize as readily and therefore may not enter the air but depending on the compounds Ksp, it may dissolve into the water.

Question 14

5. Understand the definition of and how the following properties effect chemical fate and transport: f. Henry’s Law:

Answer 14

f. Henry’s Law: Under equilibrium conditions, the partial pressure of a gas above a liquid is proportional to the concentration of the chemical in the liquid.
o It is useful in estimating the degree to which an organic compound will evaporate out of water.
o Higher the Henry’s Law constant, the more likely it is to evaporate from water. If henry’s law constant is 5x higher than that of another compound, it will evaporate 5X faster.
o If ethanol is mixed with water, henry’s law tells us that the VP will be reduced by it dissolving in water.
o There is a balance between VP and water solubility, the VP of a compound wants it to evaporate, while water solubility wants it to stay in the water.
o Henry’s law constant is equal to the vapor pressure of a compound divided by its water solubility (H=VP/S). It is therefore directly proportional to the VP and inversely proportional to the water solubility.

Question 15

5. Understand the definition of and how the following properties effect chemical fate and transport: g. Bioconcentration factor:

Answer 15

g. Bioconcentration factor: tells you how much of a compound enters the organism.
o BCF=Corganism/C, where Corganism is the concentration in organism (mg/kg or ppm) and C is the concentration in the water (ppm).
o If 10x more of the compound is found in the organism, then the BCF=10.
o If 10x more is found in the water than in the organism, then the BCF=0.1.

Question 16

5. Understand the definition of and how the following properties effect chemical fate and transport:
   h. Biodegradation potential:

Answer 16

h. Biodegradation potential: The ability of microbial and other metabolic processes to degrade an organic chemical.
o It can be the result of an organism using the chemical as a food source (to derive energy).
o General factors that favor biodegradation are water solubility, OH NO2 NH2 acids, branched vs. straight chain, aliphatic vs. aromatic, etc.
o It is easier for microbial enzymes to break chemical bonds in the vicinity of polar areas, such as those occupied by OH groups. It is also easier for a polar/water soluble compound to become dissolved (will be established at a higher concentration) in the polar environment occupied by microorganisms, so more material is effectively available for degradation.

Question 17

5. Understand the definition of and how the following properties effect chemical fate and transport: i. Volatility

Answer 17

i. Volatility: ability of a chemical to evaporate and enter vapor form.
o Characteristics of highly volatile chemicals: low MW, high VP.

Question 18

Know how to define LD50, and draw and properly label the axes on an LD50 curv

Answer 18

 LD50 describes the relative potency of a chemical.
 Dose (mg/kg body weight) required to kill 50% of an exposed test population
 X-axis is dose of a chemical and may be in a logarithmic scale but with the unit mg/kg body weight of individual.
 The graph shows a dose-response curve, which represents the quantitative relationship between the concentration of a xenobiotic in the body and the magnitude of the biological effect that it produces, which is usually a function of the amount of the xenobiotic that a person is exposed to
 Generally a high LD50 for one substance indicates that that substance is not as toxic as another substance with a lower LD50.
 However, the LD50 is NOT a complete description of toxic potential; a compound may have a high LD50 and still have the ability to cause negative impacts (cancer, birth defects, liver toxicity, CNS impairment, etc.-these are examples of endpoints that may be more relevant to ED50).
 Some chemicals can have both therapeutic and toxic effects, where too low of a concentration can have negative effects and too much can also have negative effects (Vitamin A, for example), need moderation.

Question 19

7. List 5 reasons why individuals in a population might respond differently to when exposed to the same dose of a particular chemical.

Answer 19

 Gender, age, health status, previous exposure, body weight, lipid content, genetic factors/sensitivity, social factors (placebo effect), previous exposures/tolerance/sensitivity, rates of metabolism, interactions with other chemicals/drugs already in the body

Question 20

8. Discus the use of genomics in the identification of subpopulations, and the practical and ethical issues raised by its application in the management of environmental and workplace health.

Answer 20

• Pharmacogenomics or toxicogenomics offer the potential to identify and protect subsets of people predisposed to toxicity from chemicals or drugs or who have different chemical/drug sensitivities.
• No equal opportunity and potential for unethical targeting of these populations for various reasons (healthcare, advertising drugs, life insurance, etc.)
• Think of a bell curve and the “outliers” due to a range of different factors (genetic factors, weight, gender, etc.) and how we have a diverse population with some that are very sensitive and others that are not.
• Can determine that a portion of the population are particular sensitive while others are not…the identification of these subpopulations can lead to ethical issues and discrimination within a population.

Question 21

9. Understand the difference between acute, sub-acute, and chronic and cub-chronic exposure.

Answer 21

 Acute: single, one-time exposure for less than 24h
 Sub-acute: repeated exposures for 1 month or less at doses lower than can cause immediate death, observe for effects
 Sub-chronic: long term exposure (1-3 months) at low dose
 Chronic exposure: long-term exposure (>3 months) to levels that capable of causing immediate death: look for effect of a lifetime exposure.

Question 22

10. Define ED50

Answer 22

10. Define ED50: the (effective) dose required for 50% of an exposed population to display a measured endpoint (specific response) (ex. sleep, excitability, birth defect, improved agility, whatever the endpoint is determined to be).
    • The x-axis will be the same as the LD50 curve, in mg/kg body weight, while the Y-axis will be the measured response to whatever endpoint you are studying, probably in percentages (50% of that endpoint is measured).

Question 23

11. Describe how simultaneous exposure to multiple chemicals can result in
    a. Additive effects:

Answer 23

a. Additive effects: (1+1=2); the combination of 2 chemicals will produce an effect that is equal to their individual effects added together

Question 24

11. Describe how simultaneous exposure to multiple chemicals can result in
    b. Antagonistic effects:

Answer 24

b. Antagonistic effects: (1+1=

Question 25

11. Describe how simultaneous exposure to multiple chemicals can result in
    c. Synergistic effects: (

Answer 25

c. Synergistic effects: (1+1+>2); the combination of 2 chemicals produces an effect that is greater than the sum of the effect that either chemical would have singularly (greater than their additive effect).
 Keep in mind that chemicals can have different target organs and two chemicals can have independent effects on the different target organs. If chemicals have similar target organs, they are more likely to have additive, antagonistic, or synergistic effects based on competing or non-competing mechanisms.

Question 26

12. Describe the process and consequences of sensitization caused by repeated exposure to a chemical sensitizer.

Answer 26

• Numerous chronic exposures cause no apparent effect but later exposures (at similar or even lower dose) causes a reaction because of the immune response triggered by previous exposures
• More exposure, more reaction each time.
• Most common in skin exposures
• Sensitization is a result of an immune response to that chemical. The individual is first insensitive because he/she has yet to build up antibodies that can detect and respond to that chemical, accompanied by inflammation. Once sensitized, it can take very little chemical to cause a response. Potentiation takes place without an immune response. It usually will cause a second chemical to be much more toxic (it will take less of the second compound to be toxic, than in the absence of the potentiating chemical). Most commonly, potentiation is the result of the first compounds ability to interfere with the metabolism of the second. For example, it might decrease the effectiveness of the enzymes responsible for metabolism of the second compound, resulting in a higher blood level of that compound over a longer period of time. Or in another case/example, the second compound might only be toxic when metabolized, and the first compound induces the production/concentration of those enzymes. Increasing the enzyme levels will increase the rate/amount of metabolism of the second compound to a toxic product. As for “delayed” toxicity, this is seen when the target organ/system is damaged due to the exposure, but the full degree of damage does not occur directly/shortly after the exposure. This can occur as a result of long-term (chronic) exposures but sometimes also as a result of an acute exposure. You can find instances (the following are only examples, and others are possible) as “delayed” toxicity in an immune/sensitized response; a chronic exposure to an enzyme inducing chemical, with toxicity only upon exposure to a second compound; or by effects in a diseased organ observed well after the beginning of long term chronic exposure.

Question 27

13. List and describe the different routes by which a human can be exposed to an environmental chemical, and how the routes differ.

Answer 27

• Key point: Exposure factors effect toxicity, such as exposure frequency, exposure duration, and exposure concentration
• Absorption across barriers controls entry
a. Inhalation: Lung has a high surface area and therefore high exposure route potential.
• The blood circulating in the lungs pick up the toxins that are absorbed and transport them throughout the body.
• Blood from the lungs can travel to the GI tract or into the bloodstream prior to being filtered by the liver and therefore can have more deleterious effects on the body.
• Lipid soluble favored (low water soluble)
• High VP favored
b. Ingestion: Ingested toxins are diluted by stomach content
• Generally a slower uptake by the small intestines than from the lungs
• Passes through the liver before traveling through the system which is an opportunity to metabolize the toxic compounds to diminish their harmful effects on the body
c. Dermal Contact: Absorption differs for different chemicals and generally the skin provides a barrier for toxins to get into the body but can absorb still, at a lesser rate of uptake.

Question 28

14. Understand and be able to describe the concept of toxicity “threshold”.

Answer 28

• The minimum amount necessary for a reaction to occur
• Ex. The dose-response curve: no response is seen until the threshold dose is reached
• Eventually a maximum effect will be seen, where adding more dose will not elicit a larger reaction

Question 29

15. Be able to describe how metabolism and excretion function to limit the duration of toxic effect.

Answer 29

• Metabolism is the major mechanism for terminating the biological activity of chemicals and is therefore frequently the most important factor in determining the duration and intensity of the pharmacological response to a chemical.
• The liver is the primary site of metabolism and converts non-polar compounds into polar compounds
• Biotransformation is the chemical modification made by an organism on a chemical compound and is the process by which nonpolar toxic compounds can be converted to polar so that they can be excreted through the urinary tract.
• Therefore, the faster a toxin is excreted; generally the lower its toxicity was among other conditions.