Health & Environment

What is meant by sustainable development? 

meeting the needs of the present w/out compromising future generations to meet their own needs

cholera to chloroform as an example of environmental risk transition 

solve a problem w treatment → chlorine

chlorine combines w organic matter → chloroform

chloroform → is a DBP causing new issues

sustainable development key components

limit pop growth, maximize benefit for greatest number, resource utilization

• yield for renewables, limit, non renewables, prevent pollution

Percival Pott 1775

determined chimney cleaners association with soot (carcinogens) caused cancer

John Snow

father of epi, used maps to show cholera’s spread across 1850s London

• mapped loww, high, and no exposure areas

• found contamination from Southwark and Vauxhall company

prevalence

proportion of population w existing disease at given time

incidence

new cases of disease during given time period

• preferred measure for risk factor studying

prevalence calculation

#existing cases / #in study population

risk calculation

new cases / # people at risk

stated per amount of observation time (risk in population over ten years)

surveillance

track and compare disease rates across places, diseases, and time

surveillance examples

blood lead levels, cancer registries, surveillance biomonitoring, veteran health registry (example of surveillance in exposed population)

surveillance biomonitoring

use of monitoring to document rates of exposure or disease in populations

ecological study

utilize group level aggregated rates

crude rates

these rates represent different populations, or same population at different times, meaning they’re not comparable

• can’t compare bc changes may obscure differences

how age-adjusted or standardized rates make populations comparable

use a third population as a reference

specific rates separated by what

gender

ecological fallacy

trends occuring in group-level data not necessarily true at individual level

• may produce relationship that wouldn’t be seen if looked at individuals

ecological study

epi study using group-level data instead of individual — adjusted mortality or morbidity rates for disease compared across diff populations 

• easier to get info, cost effective, hypothesis generating

• single exposure is assigned to full group

what do case control studies identify

comparing the exposure of ppl w and without the disease

Tuskegee Institute

studied 600 black men, 2/3 w syphilis, families got some compensation and care after 10 million settlement, Clinton formally apologizes

environmental epi challenges

long latency periods, exposure to many harmful exposures, misclassification, modest relative risk 

what’s considered a systematic error during the conduct of a study

bias

odds ratio calculation

odds that a case was exposed / odds that a control was exposed

what studies are useful for risk factor assessment of rare diseases

case control

what study is used for common exposures or rarer occupational exposures (paper-work providing)

cohorts

relative risk RR

provides estimate of association; prevalence of disease in exposed/prevalence in non-exposed

• RR greater than 1 indicates exposure may be harmful

• 1 is no association

• <1 disease is less common in exposed compared w non-exposed

• done for cross sectional and cohort

what epidemiological study recruits based on participants disease status

case-control

odds ratio

quantifies association between exposure and case status or an appropriate surrogate for RR

what do cohort studies compare

incidence rates

Temporality

exposure occurred prior to the development of disease; this must be true to establish causality

in ecological studies, how many exposure values are assigned to the group

one — to properly compare environmental exposure across groups

establishing causal connection

association strength, inter-study consistency, temporality, biological plausibility, dose-response

deterministic effects 

an effect whose severity depends on dose

hazard quotient

ratio, comparing average daily dose to a reference dose

stochastic effects

an effect whose probability depends on dose; there is no safe threshold level without some risk

e.g. radiation

goals of risk assessment

quantitative summarizing of hazards associated w exposure, bridge understanding gap btwn knowledge of hazards and its human impact, create best estimates of possible health hazards, regulatory supporting evidence

risk communication

exchange of information about a hazard between experts and those affected

precautionary principle

warnings of harm from an activity/substance before clear proof of harm — not followed in US very well

cradle-to-cradle approach

hazardous waste management style where resources may be reused or repurposed

cradle-to-grave

materials need to be documented from origin point through manufacturing to final disposal

exposure pathway

process contaminant travels from its source to the exposed population, ends w exposure

• source → transport → exposure point

exposure route

method a contaminant enters the body: dermal absorption, inhalation, ingestion

• exposure point → exposure route

teratogen

defects coming from exposure between conception and birth

• e.g. drugs/alcohol

biomagnification

substances become concentrated as they move up the food chain reaching lethal doses in higher trophic levels

bioaccumulation 

buildup of a chemical in an organism’s tissues over lifetime as they consume more than they excrete

e.g. mercury, DDT, PCBs

quantifying estimates of exposure methods

measuring & modeling

proxy for human dose

indirect measures used to estimate internal exposure from toxicant that affects a body or body part when direct measurements or impossible — closer one is to source of contamination = better proxy

e.g. pollutant levels measured by water analysis of creek in backyard 

quantifying exposure requirement

typically requires knowledge of fate and transport

• need to measure conc. at exposure location AND modeling of human behavior

biologically effective dose meaning

the amount of contaminant that’s available to interact w the body

• the fraction of the dose actually interacting w tissues/organs/etc

• the part of the dose that reaches/affects sensitive tissue

standard units of absorbed dose

mg / (kg x day)

typical axes when plotting a dose-response relationship

x = dose

y = % response

• can include threshold

threshold meaning (in a dose-response relationship)

highest dose at which no toxic effect occurs 

• doses at or below threshold are considered to have zero toxic effect

• threshold of 0 = no safe dose

xenobiotic

foreign chemical to the body

toxicokinetic sequence

xenobiotic absorption, blood-vehicle distribution, metabolism/ excretion/ storaged

toxicokinetics

combined process absorption, distribution, metabolism, storage, and excretion of toxicants

synergism

interaction of multiple exposures produces a combined effect greater than the sum of the separate effects; result is an enhanced toxic effect

antagonism

interaction of multiple exposures produces an effect that is less than expected from the sum of the separate effects; interference

biomarker (and examples)

LD₅₀

describes a dose that is lethal to 50% of the population

3 general categories of enviro hazards

chemical: metals, acids, solvents

physical: noise, heat, radiation

biological: virus, bacteria, fungi

Conceptual Model of Exposure (toxicology) different components

body burden definition

toxicokinetics vs toxicodynamics

human envelope

boundary that separates the interior of the body from the exterior environment

bioconcentration tendency as a chemical characteristic

direct absorption of contaminants; biological consequence of a chemical’s lipophilicity

e.g. lipophilic chemicals are drawn to fatty tissues

physical-chemi properties that govern their fate in the environment

volatility, solubility, vapor pressure, water solubility, molecular size and shape, hydrophobicity, chemical decay

• media involved: locations traffic, nearby food and drink consumption, contact w contaminated objects

biomonitoring

process of measuring the body burden of toxic chemicals

• usually from blood, hair, saliva, urine, breast milk

environment exposure

occurs when environmental contaminant contacts human envelope 

pathogen definition

infectious agent causing disease

pathogenic agents of concern

worms, protozoa, single-celled bacteria, fungi, virusesm prion

what are reasons for infectious diseases re-emerging as significant concerns for human health?

poor surveillance and prevention infrastructure, increasing urbanization, treatment resilience, humans migration, climate change, pathogens and vectors are resilient,

reservoir meaning

place where a pathogen normally lives, multiplies, and depends on for survival

• contaminated water, ppl, animals

zoonosis and its methods of transmission

type of infectious disease transmitted from animals to humans

• transmission: bite, scratch, inhalation, ingestion, skin contact

vector

living transmitter of pathogens, vector borne disease

fomite

object passively transmits pathogens

• shared cup, keyboard, shared toys

mechanical vector

physical vector

• syringes, flys

infectious disease transmission via close proximity or contact

airborne transmission

non-fecal organisms

in water or soil, guinea worm, bacillus anthracis (anthrax) , spores (tetanus)

fecal-oral transmission

soil: common where latrine pits are used for waste

hands: concern for children who don’t wash hands

hand-to-mouth: adults when eating and smoking

waterborne: untreated sewage into water sources

fecal-oral pathways and foodborne transmission

person ingests pathogens from feces originating from a person w an infectious diarrheal disease

• water w contamination used to prepare food

• contaminated veggies from soil

foodborne pathogens in developed countries

usually not from human feces, but from animal feces, soil pathogens, human skin, mechanical vectors like insects

biological vector

host species that transmits disease to another host species

vector-borne transmission management

reduce vector population

• reduce stagnant water, manage garbage, release sterile mosquito males, pest control

vaccines against pathogens

produces immune response while bypassing the illness itself 

immune system against pathogens

herd immunity

immune malfunction and its relation to allergies

characteristics of autoimmune disease

hygiene hypothesis and its implications

children today are exposed to less pathogens and immune system doesn’t differentiate between self and truly foreign pathogenic agents — clean environments reduce’s exposure to pathogens and increase autoimmune and allergic diseases 

what are some strategies that have been used for managing transmission of disease?

isolation vs quarantine

isolation: seperate of ppl who have infectious illness

quarantine: seperation of ppl who’ve been exposed to infectious agent and may become ill

link between infectious disease and cancer

can increase cancer risk w chronic irriation —> cell proliferation

known infectious causes of cancer

gov agencies managing infectious diseases and their roles

CDC: develops guidelines, prevents incoming diseases, surveillance, research

FDA: ensure safety and efficacy, regulate food/drugs

environmental health and infectious disease scope

focus is on infectious diseases that require an environmental mode of transmission

• waterborne, foodborne, zoonotic, vector borne diseases