Week 2-3 Flashcards
Environmental Health
Aspects of human health (quality of life) that are determined by physical, chemical, biological, social, and psychosocial factors in the environment
Disability-adjusted life years (DALY)
Estimation of total numbers of years lost due to specific causes and risk factors at the country, regional and global levels
Years of life lost (YLL)
years lost due to premature mortality
Years lived with disability (YDL)
years lived in less-than-ideal health
Global Burden of Disease (GBD)
quantifies health loss from hundreds of diseases, injuries, and risk factors, so that health systems can be improved and disparities can be eliminated
Limitations of GBD
- Exposure-outcome pairs not included
- Uncertainties in exposure assessments and concentration-response relationships
- Categorizing or dichotomizing a health continuum
- Disability weights
Population attributable fraction
Amount of disease/death avoided in the population if exposure was removed
Exposure-response relationship
How does health risk change as exposure changes?
Prevention Paradox
a large number of people at a small risk may give rise to more cases of disease than the small number who are at a high risk
ROSE idea 1
Subtle shifts in risks can have a substantial impact on health.
ROSE idea 2
A large number of people at a small risk give rise to more cases of disease than the small number who are at a high risk (PREVENTION PARADOX)
ROSE ideal 3
There is no known biological reason why every population should not be as healthy as the best
Precautionary principle
precautionary measures should be taken even if a cause-and-effect relationship is not fully established scientifically
Acute
Short-term “bursts” of exposure (hours to days)
higher concentration and (maybe) immediate symptoms
Chronic
Longer-term periods of exposure (years to lifetime)
Lower concentration, longer latency period
Exposure route
the way a substance enters the body
Three routes of exposure?
Dermal, inhalation and ingestion ((also mother-fetus transmission)
Human barriers to environment
GI tract, Respiratory tract, skin
Exposure pathway
The physical course a pollutant takes from the source to the subject: Emission > movement of emission > exposure > dose > effect
Three Key Ideas in Exposure Assessment
- Concentrations vary in time
- Concentrations vary from place to place
- People move around
Direct exposure assessment
Personal measurements,
biomarkers
Tradeoffs of direct methods
-Better estimate of true exposure
-$$$ and time consuming
-High demand on participants
-not feasible on large scale
tradeoffs of indirect methods
-poorer estimate of true exposure
-less $$$ and less time consuming
-little to no participant demand
-applicable to large pop
indirect exposure assessment
Area measurements
Questionnaires
Models
Biomarkers
Measure pollutant of metabolite in biological material (exhaled breath, urine, blood, teeth, hair)
-est dose and includes multiple routes of exposure
-can be intrusive and interpretation can be difficult
Epidemiology
study of the distribution and determinants of disease in humans
Randomized control trials
Randomly allocate participants to an intervention or control group
Cross-sectional
Assess exposure and outcome at a single point in time
Cohort Study
Identify participants who do not have the disease of interest, and observe them over time to assess new cases of the disease
Case-control
Identify participants based on disease (outcome), then determine who previously had the exposure
Effect estimates
Measures of association (relative risk & odds ratio)
Toxin
A compound of natural origin that exerts notable adverse effects on biological systems
Toxicant
A synthetic compound that exerts notable adverse effects on biological systems
ADME
four basic steps that a toxicant goes through when it enters the body: absorption, distribution, metabolism, excretion
What does it mean when we say that a toxicant has “a threshold”?
This means there is a range of exposures/doses at which the health effect(s) do not occur
Why is the presence or absence of a threshold so important?
thresholds imply that health risks can be eliminated without entirely eliminating the pollutant/chemical/product
What is a supralinear relationship?
a change in exposure/dose at the low end of the exposure/dose distribution causes a larger change in the health outcome than an equivalent change in exposure at the high end of the distribution
Lethal Dose 50
The amount (dose) of a chemical which produces death in 50% of a population of test animals to which it is administered
No observed adverse effect level (NOAEL)
The highest dose at which the adverse effect is not observed
Lowest observed adverse effect level (LOAEL)
The lowest dose at which the adverse effect is observed
(PoD) point of departure
The dose at which “bad things start to happen
Reference dose
acceptable levels of exposure to chemicals/pollutants, before bad things start to happen (cliff example)
Hazard
something capable of causing an adverse effect
Risk
probability that thehazardwill cause an adverse effect under specificexposureconditions
Risk assessment
the process by whichhazard,exposure, andriskare determined
What are the steps of risk assessment?
1.Problem formulation
2.Hazard identification
3.Dose-response assessment
4.Exposure assessment
5.Risk characterization
Risk management
the process of weighing policy alternatives and selecting the most appropriate regulatory action based on the results ofrisk assessmentand social, economic, and political concerns
What does it mean for an agent (chemical, product, activity, etc.) to be designated as IARC group 1?
A substance is defined as a ‘known human carcinogen’
Perceived risk
An intuitive judgment about the nature and magnitude of a health risk
List some of the key pollutants or pollutant categories
Particulate matter
Ozone (O3)
Sulfur dioxide (SO2)
Nitrogen oxides (NOx = NO and NO2)
Carbon monoxide (CO)
List the major health effects through which ambient air pollution and household air pollution contribute to the global burden of disease
52% cardiovascular and circulatory diseases, 12% respiratory and other infections; ambient air pollution contributes to a huge burden on cardiovascular health
Carbon Monoxide
Colorless, odorless, tasteless gas produced by combustion (gas stoves, space heaters)
Radon
Colorless, odorless, radioactive gas (uranium in soil breaks down to form radon)
Describe some of the reasons that pesticides are used.
Designed to kill living things
Pesticides are hazardous substances intentionally added to our environment.
** they kill off hosts that are responsible vetors of spreading disease
Organochlorine Insecticides
-Low volatility, chemically stable, slow degradation
-more stable and degrade more slowly in the environment
-persistent in environment
DDT
-A Organochlorine Insecticide
-Persistent in enviroment n humans (2.5 yrs of half-life in soil)
-Acute effects:Irritability, dizziness
-Chronic effects:Endocrine disruptor, reproductive effects,carinogenic
Rachel Carson
published the ‘Silent Spring’ on the environmental effects of DDT and as a result was banned > cause millions of Africans to die from malaria as DDT was one of the most effective insecticide against malarial mosquitoes
Organophosphorus (OP) Insecticides
-Responsible for the majority of pesticide poisonings and deaths
-less persistent in the environment but also more acutely toxic in humans
Sarin
A particularly toxic organophosphorus compound
that is much more potent
Carbamate Insecticides
-Less acutely toxic than OPs and less poisonings
Pyrethroid Insecticides
Synthetic versions of naturally occurring chemicals pyrethrins
-Less acutely toxic than OP pesticides
Identify the primary route of pesticide exposure for non-occupationally exposed populations (i.e., the general public).
Residue on food - conventional food may contain more synthetic pesticide residues
What are the 3 pesticide exposures?
-dietary ingestion
-dermal
-inhalation
Spray/pesticide drift
A potentially important source of exposure for communities close to agricultural activity
