Environmental Health Test 1
Closed cohort study – when to use?
a well-defined group of persons is followed over time as events of interest occur; can be conducted prospectively (longitudinal– follow-up after exposure and continue often until death)or retrospectively (access roster of exposed and non exposed)
Open cohort study – when to use?
population is monitored to collect the number of incident events and the amoutn of person-time at risk; youcan add people to the cohort. It is typically used in occupational settings where the number of jobs is constant but the individuals in those jobs change over time
Cross sectional study – when to use?
information on exposure and outcome are collected at the same time, generally using the same questionnaire; often uses self-reporting
Case control study – when to use?
participants are defined on basis of presence (case) or absence (control) of an outcome of interest; cases and controls are generally matched according to criteria such as age, gender, ethnicity etc and exposure is determined retrospectively
Selection bias
selection of study subjects depends on both the exposure and the outcome of interest
Information/observation bias
the measurement of either the exposure or the outcome of interest depends on the true value of the other parameter
Odds Ratio
the measurement of association between exposure and the outcome used in case-control studies; it is the ratio of odds in favor of the exposure of the cases (A/C) to the odds in favor of exposure among the non-cases (controls: B/D)
A/C: B/D
Relative risk
measure of association used in cohort studies; the ratio of the incidence rate of a disease/health outcome in an exposed group to the incidence rate of the disease or condition in a non-exposed group
A/A+B : C/C+D
What do relative risk #s mean
RR>1 the risk of disease is greater in the exposed group than in the non-exposed group
RR<1 possible protective effect
Epidemiologic Triangle/Causality
Host (a person or organism that harbors an infectious agent under natural conditions) : Agent (a factor whose presence or absence is essential for disease occurrence): Environment (domain, external to human host, in which disease-causing agents may exist, survive, or originate)
causality
certain criteria needs to be taken into account in the assessment of a causal association between an agent factor (A) and a disease (B)
* strength * consistency * specificity * temporality * biological gradient * plausability * coherence
Hill’s Criteria of Causality
Strength- strong associations are more likely causal; weak associations may be confounding thus requiring a stronger determinant of disease (ex- air pollution and daily mortality)
Consistency: replication in different populations or study designs, consistency across strata (persons, places, times, circumstances) ex is smoking and lung cancer
Specificity: one to one relationship between cause and effect; difficult to gage when one-to-several relationships exist
Temporality: cause must precede effect and latency period must be appropriate for outcome of interset
Biological Gradient: dose-response relationship should be exhibited; nature of relationship; chance for measurement error
Plausibility: existence of a biologic mechanism
Environmental toxicology
examines how environmental exposures to chemical pollutants may present risks to biological organisms, particularly animals, birds and fish
Poison/Toxicity
Poison is any agent capable of producing a deleterious response in a biological system
Toxicity is the degree to which something is poisonous, related to a material’s physical and chemical properties
Dose
the amount of a susbstance administsered at one time – various types (exposure, absorbed, administered, total, external, internal, biologically effective)
Dose-response relationship
correlative relationship between the characteristics of exposure to a chemical and the spectrum of effects caused by the chemical; a dose-response curve is a graph used to describe the effect of exposure to a chemical or toxic substance upon an organism sch as an experimental animal (you can also have an individual dose response curve and the ultimate measure of toxicity is cancer/non cancer and then death)
Additive
1 + 1 = 2
the combination of two chemicals produces an effect that is equal to their individual effects added together
synergism
1 + 1 > 2
combined effect of exposures to two or more chemicals is greater than the sum of their individual effects
Potentiation
0 + 1 –> 0 + 1.5
one chemical that is not toxic causes another chemical to become more toxic
antagonism
1 + 1 < 2
two chemicals administered together interfere with each other’s actions or one interferes with the action of the other (reduces the efficacy)
name the chemical toxicity factors
*route of entry into the body
*received dose of the chemical
*duration of exposure
*interactions that transpire among multiple chemicals
*individual sensitivity
exposure duration
acute: usually la single exposure for less than 24 hours
subacute: exposure for one month or less
subchronic: exposure for one to three months
chronic: exposure for more than three months
health effects
local effects: damage at the site where the chemical first comes into contact with the body (ex: poison ivy)
systemic effects: generalized distribution of the chemical throughout the body by the bloodstream to internal organs (ex: chicken pox)
target organ effects: some chemicals may confine their effects to specific organs

cancer vs noncancer

hazardous waste
liquid, solid, contained gas, or sludge wastes that contain properties that are dangerous or potentially harmful to human health or the environment — includes discarded commercial products (ex- cleaning fluids or pesticides) and by-products of manufacturing processes
* developed world generates most of the toxic wastes
sources of hazardous waste
* home use – pesticides, cleaning products, automotive products, painting supplies, & other flammable/nonflammable products
*medical waste – chemicals, infectious agents, & radioactive materials – production or testing of biologicals
* industrial hazardous waste – heavy metals from plating operations, toxic chemicals, solvents, & residues from the manufacture of pesticides (Love Canal)
* radioactive wastes – spent nuclear fuel and tailings from uranium processing
* mining wastes & extraction wastes – toxic chemicals left over from mining operations include acids and heavy metals
characteristics of hazardous waste
*ignitable (liquids, non-liquids, compressed gas, & oxidizers)
* corrosive (aqueous – pH less than or equal to 2 or pH greater than 12.5)
* reactive – includes chemicals that are unstable at STP, highly reqctive with water
* toxic – harmful or fatal when ingested or absorbed (ex- contain mercury or lead); when land disposed, contaminated liquid may leach from the waste and pollute ground water
National Priorities List (NPL)
EPA’s list of the most serious uncontrolled or abandoned hazardous waste sites in the US identified for possible long-term remedial action under Superfund
– scored based on the HAzard Ranking System & updated at least once a year (score of 28.5/100)
Superfund Cleanup Process
1. preliminary assessment – is a threat posed to human health & environment? collect readily available information; determine whether further investigation is necessary
* site inspection – provide data necessary for HRS scoring; samples usually collected to determine what hazardous substances are present
* NPL Site listing process – – ???
– 4 pathways (groundwater migration, surface water migration, soil exposure, air migration)
* remedial investigation/feasibility study – collect data to characterize site conditions, determine, the nature of the waste, assess risk to human health & environment, & conduct treatability testing to evaluate the potential performance & cost of the treatment technologies that are being considered
– Feasibility study mechanism to develop, screen, & evaluate alternative remedial actions
Conceptual Site Model
1. source of contaminant
2. pathways of environmental transport
historical context of water
*Early-mid 1800’s: annual death rate from waterborne typhoid fever averaged 30/100,000; users of municipal public water supplies had a chance of 1/4 to 1/5 to die from cholera, typhoid, or other enteric diseases (infections enter body through mouth/intestinal system)
* late 1800s: pollution concners in Boston adn NYC led to Boards of Health; rise of sanitary/PH engineers
1880s: establishment of engineering experiment stations
current drinking water challenges
* increasing population – 50% of world’s pop resides in metro areas
* climate change – regional effects – drought, flooding, changes in precipitation patterns
* water sources- issues concnerning protection, new sources, depletion
~ by 2015, 36 US states estimated to face serious water shortages
~ by 2025, 2.5 billion in 48 countries will experience water stress or water scarcity
* emerging contaminants
water stresss
1,000-1,700 m^3 renewable freshwater per person/year
water scarcity
<1,000 m^3 renewable freshwater per person/year
water infrastructure
the public water system in US – delivers water for human consumption through a pipe or pipes
– 57,000 community water systems
– 128,000 non-community water systems
water infrastructure needs
– aging infrastructure
– $335 billion estimated for pipe, treatment, storage, source, and other infrastructure needs for the 20 years (as of 2009)
– 35 states submitted “shovel-ready” infrastructure projects – most were 2-30x greater than the grant money to be received
– security needs!
[image]
how much of the world’s water is freshwater vs saltwater
97% saltwater (saline/oceans); 3% freshwater
of the earth’s fresh water how much is usable?
surface water
rivers, lakes & reservoirs, oceans (but this requires desalination)
groundwater
aquifers (sealed with no real time surface influences)
springs (groundwater under surface influence)
unconfined aquifers
the upper surface of saturated zone is free to rise and decline; when it rains the water level will rise — a pollution concern that will possibly permeate through the soil
confined aquifers (aka ?)
aka artesian
– permeable layer confined by upper and lower layers that have low permeability (like rock, clay)
water is usually under pressure
sources of water contamination
*vandalism/terrorism
*agricultural – animals, fertilizers, pesticides, manure, runoff
*commercial – transportation related facilities, dry cleaners, golf courses, medical/research facilities
* industrial – chemical/electronic manufacturing, foundries, mining, petroleum production/storage
*residential – fuel oil, lawn maintenance, septic, sewer lines, swimming pools, household hazardous products
* other – hazardous waste landfills, incinerators landfills, sewer lines, road deicing, transfer stations
goals of water treatment
1. taste and odor
2. contaminants
3. microbiological organisms
water quality reporting parameters
– regulated contaminants
– radioactive contaminants
– unregulated chemical contaminants
– contaminants subject to an action level
– disinfection byproducts
– microbial contaminants
drinking water treatment processes
1. intake- tunnels, pump stations, shafts
2. clarification and filtration
3. disinfection – chlorine, UV treatment, chlorine dioxide, ozone
4. distribution
clarification
physical removal process of particles in water — chemical conditioning, aggregation, physical separation
filtration
removal of particulate matter, turbidity, and pathogens from drinking water; selection based on budget, operational flexibility, space rquirements, target contaminants
types of filtration
– sand filters
– activated carbon (powdered/granular)
– membrane filtration (not effective for dissolved liquids, disinfection byproducts, taste/odor, total organic carbon)
4 major drinking water disinfection techniques
1. free chlorine – most widely used for water & wastewater
+ powerful against bacteria, viruses, giardia; low cost and low maintenance
– forms carcinogenic disinfection byproducts; not effective against Cryptosporidium; safety concerns w/transportation and handling
2. chlorine dioxide – introduced for taste and odor control
+ improved taste & odor control; reduced color problems
– aggressive regulatory monitoring requirements related to health issues; higher cost; need to store multiple chemicals; need for more complicated analysis methods and skilled operators
3. UV light
+ physical process (no chemicals), taste and odor not affected, no toxic byproduct; residence time in the seconds (smaller reactors – lower costs); effective against many chlorine-resistant pathogens
– no measurable chemical residual to monitor performance; no standards for UV dose; no mechanism to protect finished waster as it moves through distribution system
4. Ozone- over 300 plants in US use
+ removes taste and odor compounds; aids in coagulation and microflocculation; increases TOC removal and improves filter performance; provides strong disinfection; decreases DBP formation by allowing chrloine feed later in process at LOWER DOSE
– can’t be used as final disinfectant as highly unstable in water; high energy and chem costs; high equipment capital and maintenance costs
risk perceptions
intuitive risk judgments used by citizens to evaluate hazards
– perceived risk is quantifiable
aware versus unaware
dread versus non-dread
also dread & unknown
– familiarity, catastrophic potential, control, equity, and knowledge are important factors
-increases with lack of control
voluntary versus involuntary
voluntary: more unknown, less dread
involuntary: more unkonwn, more dread
– acceptability of risk from an activity is proportional to benefits from the activity
– people accept risk from voluntary activities 100 times more than involuntary
current world and US populations
7.14 billion US (hit 7 billion last year)
317.4 billion world
population distribution by age
– before 2000 young outnumbered old
– population moer than doubled for people > 52 ; today 3 billion in 1960 and 7 billion 2011
– demographic transition
cost of avoiding hazards
cost of product substitution
temporal trends
why is environmental epi important
health effects
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