For Final Flashcards
Toxicity
the degree to which a chemical substance or a particular mixture of substances can damage an organism
can refer to the effect on a whole organism as well as the effect on a substructure of the organism (such as cell (cytotoxicity) and the liver (hepatoxicity)
Toxicology
the study of harmful effects of substances on the environment, humans, animal health (the science of safety)
harmful effects on living things
Ecotoxicology
impact of exposures on population/communities/ecosystems
central concept of toxicology is that the effects of a toxicant are …
…dose-dependent
Will someone definitely get sick if exposed to a harmful substance?
No
also there are periods in a person’s life when he or she may be more susceptible to chemicals
____ often determines the toxicity of a substance
the route of exposure
dermal, inhalation
“the dose makes the poison”
LD50
Toxicity can be measured by its effects on the target
The value of LD50 for a substance is the dose required to kill half the members of a tested population after a specified test duration
LD50 figures are frequently used as a general indicator of a substance’s acute toxicity
A lower LD50 is indicative of increased toxicity
Usually determined by animal tests (sometimes conflated w the concept of mouse unit (MU)) (the amount of toxin required to kill a 20g mouse in 15 min)
usually expressed s the mass of substance administered per unit mass of test subject (typically as mg per body mass (usually kg))
*The choice of 50% lethality as a benchmark avoids the potential for ambiguity of making measurements in the extremes and reduces the amount of testing required…however this also means that LD50 is not the lethal dose for all subjects; some may be killed by much less while others survive doses far higher
Limitations of Measuring Toxicity
- lethal dosage often varies depending on the method of administration; for instance, many substances are less toxic when administered orally than when intravenously (opioid epidemic relevance)
- length of exposure (time)
- age/life stage of organism exposed
- LD50 somewhat unreliable and results may vary greatly between testing facilities due to factors such as the genetic characteristics of the sample population, animal species tested, environmental factors and mode of administration
- can be wide variability between species as well (what is safe for rats may not be for humans and vice versa)
Environmental Racism
used to describe environmental injustice that occurs within a racialized context both in practice and policy
“racial discrimination in environmental policy-making, the enforcement of regulations and laws, the deliberate targeting of communities of color for toxic waste facilities, the official sanctioning of the life-threatening presence of poisons and pollutants in our communities, and the history of excluding people of color from leadership of the ecology movements”
It is a form of systemic racism whereby communities of color are disproportionately burdened with health hazards through policies and practices that force them to live in proximity to sources of toxic waste - as a result these communities suffer greater rates of health problems attendant on hazardous pollutants
Bhopal Chemical Disaster
AKA Bhopal gas tragedy was a gas lead incident in 1984 at the Union Carbide India Limited Company
was a majority US owned company
over 500,000 exposed to methyl isocyanate (MIC) gas
caused by poor maintenance and insufficient safety protocols
few if any efforts at remediation have been enacted or enforced
2 decades after initial explosion:
4,000 gas victims required hospital treatment every day
reproductive health outcomes - birth defects, genetic abnormalitties, social relationship disruption
Remaining organochlorines: CNS impairment, thyroid, liver, kidney damage, eye irritation, skin, respiratory tract, endocrine disruption
Endemic toxins (remaining heavy metals): miscarriage, nervous system impairment, behavioral + learning impairment in children, digestive tract irritation, kidney damage, infertility
Bhopal Chemical Disaster
AKA Bhopal gas tragedy was a gas lead incident in 1984 at the Union Carbide India Limited Company
was a majority US owned company
over 500,000 exposed to methyl isocyanate (MIC) gas
caused by poor maintenance and insufficient safety protocols
few if any efforts at remediation have been enacted or enforced
2 decades after initial explosion:
4,000 gas victims required hospital treatment every day
reproductive health outcomes - birth defects, genetic abnormalitties, social relationship disruption
Remaining organochlorines: CNS impairment, thyroid, liver, kidney damage, eye irritation, skin, respiratory tract, endocrine disruption
Endemic toxins (remaining heavy metals): miscarriage, nervous system impairment, behavioral + learning impairment in children, digestive tract irritation, kidney damage, infertility
What is a syndemic or synergistic epidemic?
the aggregation of 2+ concurrent or sequential epidemics or disease clusters in a population w biological interactions, which exacerbate the prognosis and disease burden
develop under health disparity, caused by poverty, stress, or structural violence and are studied by epidemiologists and medical anthropologists concerned w public health, community healht, and the effects of social conditions on health
Superfund Sites
CERCLA is informally called superfund… the act allows the EPA to clean up contaminated sites…also forces the parties responsible for the contamination to either perform cleanups or eimburse the government for EPA-led cleanup work
Love Canal
Hooker Chemical co dumped toxic chemicals
in 1950s, site was sold to become a public school
lots of leukemia, birth defects, high morbidity + mortality rates
protests began in the 1970s
in 1988 the NY dept of health described love canal as “a national symbol of a failure to exercise a sense of concern for future generations”
Epidemiological Transition
a shift from infectious diseases to chronic noncommunicable diseases being the primary cause of deaths and disability in a population
Noncommunicable diseases (NCDs)
conditions that are not contagious
most noncommunicable conditions are chronic diseases that develop gradually and last for a long time
*the percentage of deaths from NCDs in a pop generally increases with economic growth
“diseases of affluence”
- false dichotomy since NCDs are the primary cause of disease burden in adult populations globally regardless of country income level
modifiable risk factors are thought to be responsible for at least two thirds of all worldwide deaths from these conditions
NCDs that can be prevented through behavior change are sometimes called lifestyle diseases
Self efficacy
an individuals confidence in their ability to successfully complete a difficult task
The Health Belief Model States that…
individual behavior change is a function of personal perceptions of the severity of the disease, their own susceptibility to it, and their likely benefits of adopting healthier behaviors as well as perceptions about the barriers to action and their own self-efficacy to enact change
cues to action are important for triggering behavior change
Examples of NCDs
Chronic Respiratory diseases (CRDs)
Asthma
Chronic Obstructive Pulmonary Disorder (COPD)
- bronchitis
- emphysema
diabetes
other top NCDs worldwide
Digestive diseases
liver and kidney disease
CRDs
chronic respiratory diseases = diseases of airway, bronchi, and lungs (doesnt include chronic TB nor lung cancer)
Asthma
chronic, but reversible inflammation of the airways, attacks can be fatal
increasingle linked to environmental pollution
COPD
a chronic progressive disease that limits airflow and causes shortness of breath and productive coughing
causes over 3 mil deaths annually
primary risk factor: tobacco use
two of the most common presentations of COPD are bronchitis and emphysema
Diabetes
Type 1: occurs when body does not produce enough insulin
- typically sudden onset in childhood
- people w type 1 are rarely overweight
Type 2: occurs when the body develops insulin resistance and stops responding appropriately to insulin even when the hormone is still being produced
- typically gradual onset in adulthood
- considered preventable
- “diabesity” since people w type 2 are usually overweight or obese
Gestational diabetes
Diabetes + its complications have become major causes of disability and premature death in high-income and middle-income countries
between 1980 and 2015 the global diabetes prevalence rate doubled from 4.7% to 8.5% after standardizing the 1980 rates to the age distribution in 2015
The prevalence is expected to continue to climb in the coming decades to 10.4% in 2040 as more people worldwide become obese
Example of Obesity Report Cards
in 2016, Arkansas instituted an obesity surveillance campaign
a state mandate that all public schools provide weights + measurements of their students to offer parents essential info about their childrens health
model in Arkansas is being used to create new programs in states like Ma and Wy
Food Security exists when…
…people have access to enough food to be healthy, active, and productive
food security is about the distribution and affordability of food as much as it is about food production
Global Hunger Index (GHI)
a metric that estimates the burden from undernutrition in a population with a focus on young children
- residents of lower-income countries spend a much higher proportion of their incomes on food than people who live in higher-income countries spend
Food Deserts
regions where people have limited access to healthful and affordable food. May be due to having a low income or having to travel farther to find healthful food options
without access to healthful foods, people living in food deserts may be at higher risk of diet-related conditions, such as obesity, diabetes, and cardiovascular disease
#1 cited reason = lack of transport
Nutrition transition
the shift in diet and energy expenditure that coincides with economic/demographic/epidemiological changes
Genetic changes do not explain why obesity has become so much more prevalent in recent decades; it takes generations for genetic adaptations to occur, but only take a short time to change dietary and exercise habits
the nutrition transition is also related to a variety of globalization processes, including changing perceptions of beauty/health
Overnutrition
a form of malnutrition caused by excessive intake of calories and nutrients
Body Mass Index (BMI)
a measure of body composition calculated by taking weight in kg and dividing by the square of the height in meters
Obesity is associated with increased risk for many other diseases including…
type 2 diabetes, hypertension (high bp), heart disease, strokes, gallstones and other digestive disorders, back pain, arthritis of the back and hip, and several types of cancer
Adults living in high income countries are more likely to develop cancer than are adults living in low income countries… why?
The life expectancy is higher in high-income countries, so more people live long enough to develop cancer, but this trend is present even after adjusting for differences in the age structures of pops
people who live in high income countries are significantly more likely to receive a cancer diagnosis than are people of the same age who live in low-income countries
- People in low-income countries who have cancer are more likely to die from the disease than are people the same age who live in high-income countries
- diagnosed at an advanced stage
- lack of treatment access
What is the percentage of men/women who live to age 80 who will have developed some type of cancer?
30% of men and 20% of women
about 1/8 deaths worldwide each year is caused by cancer
Cancer epidemiology
across income groups
- cancer mortality rates are fairly similar across income groups
- people in high-income countries have higher likelihood of receiving cancer diagnosis and are more likely to survive
- people in low-income countries have lower likelihoods of being diagnosed with cancer and are less likely to survive - so if you can afford to get screened, your chances of survival are much greater
Types of screening
Case detection: prescriptive screening
Control of disease: prospective screening
Research Purposes
What is screening?
a type of secondary prevention in which all members of a well-defined group of people are encouraged to be tested for a disease based on evidence that members of the population are at risk for the disease and that early intervention improves health outcomes
What are some common screening tests?
pap smear for cervical dysplasia or cervical cancer
mammography for breast cancer
PSA test for prostate cancer
Fecal occult blood for colon cancer
HIV screening test
Validity of a test
refers to accuracy
Reliability of a test
may be consistent but may be innacurate
Sensitivity of a test
the proportion of people who truly have the disease who test positive for the disease
the amoung of true positives over the amount of positive results
the ability of a test to identify correctly those who have the disease (a) from all individuals with the disease (a+c)
SEN = the proportion of cases that test positive
Specificity of a test
the proportion of people who are truly free of the disease who test negative for it
the amount of true negatives over the amount of negative results
= the ability of the test to identify correctly those who do not have the disease (d) from all individuals free from the disease (b+d)
Predictive Value of Tests
PVP = proportion of positive tests that are true cases
- true positives / (true positives + false positives)
PVN = proportion of negative tests that are true non-cases
- True negatives / (true negatives + false negatives)
Screening vs Diagnostic tests
Principles in Public Health (ethical aspects of screening)
Principle: Potential Harm
Beneficience: screening program may have benefit on population level for those offered treatment but not every case will benefit
Non-malfeasance: psychological harm from false positive (before confirmatory testing), preventable deaths resulting from FN test, Iatrogenic harm from subsequent diagnostic testing, false reassurance from FN
Justice: ensure equality in uptake and linkage to care pathways among deprived and affluent poulations (harm = access)
Privacy: during screening and confirmatory testing
Autonomy: communicating risk to patients is notoriously difficult
