HCL-PHS 121 Env Health Exam 1

Ch 1 -3

What are the principle determinants of health?

• Poverty

• Population

• Poverty

List the different types of effects related to chemical mixtures

• Additive

• Synergism

• Potentiation

• Antagonism

Define additive effects of chemicals

The combination of 2 chemicals produces an effect equal to their individual effects added together

Define synergistic effects of chemical mixtures

when the combined effect of exposures to 2 or more chemicals is greater than the sum of their individual effects

Define potentiation effects of chemicals

when 1 nontoxic chemical causes another to become toxic

Describe the antagonistic effect of chemicals

when 2 chemicals given together interfere with each other’s actions or one interferes with the action of another

What are the limitations and deficiencies of environmental epidemiology

• long latency period

• low incidence and prevalence

• difficulties in exposure assessment

• nonspecific effects

What is the epidemiological triangle?

• Agent: factor whose presence, excessive presence, or relative absence is essential for the occurrence of a disease

• Host: person or other living animal, that affords sustenance or lodgment to an INFECTIOUS AGENT under natural conditions

• Environment: domain in which disease-causing agents may exist, survive, or originate

Describe the upward trend in urbanization

• 5% in 1800

• 50% in 2000

• 55% today

• Expected to reach 68% by 2025

What are factors that contribute to urbanization

• industrialization

• availability of food

• employment chances

• lifestyle considerations

• escape from political conflict

List the hazards to health associated with an urban environment

• biological pathogens or pollutants

• chemical pollutants

• availability, cost, and quality of natural resources

• physical hazards

• aspects of the built environment with negative consequences on physical or psychosocial health

• natural resource degradation

• national/global environmental degradation

Megacities

an urbanized area with 10 million or more inhabitants

• i.e. New York and Los Angeles

Carrying capacity

the maximum number of individuals that can be supported sustainably by a given environment

Food insecurity

supplies of wholesome foods are uncertain or may have limited availability

Famine

extreme scarcity of food

Explain how Hippocrates contributed to the history of environmental epidemiology

• father of modern medicine

• linked the influence of the environment to disease

Explain how Sir Percival Pott contributed to the history of environmental epidemiology

noticed the relationship between the chimney sweeping and scrotum cancer

Explain how John Snow contributed to the history of environmental epidemiology

noticed the link between the Cholera outbreak in London and their water supply, and removed the pump handles.

Define dose

the amount of substance administered at one time

Define lethal dose (LD50)

dosage causing death in 50% of exposed animals

Explain how Paracelsus contributed to the history of toxicology

• dose-response relationship

• target organ specificity of chemicals

Explain how Mathieu Orfila contributed to the history of toxicology

• Authored the work, Trait des poisons (1813)

  • Described the various poisons and their bodily effects

  • This contributed to the foundation of the forensic toxicology

Concentration and toxicity of a chemical are affected by:

• Route of entry into the body

• Received doses of the chemical

  • Duration of the exposure

  • Interactions that transpire among multiple chemicals

  • Individual sensitivity

Demographic transition

• Alteration over time in a population’s fertility, mortality, and make-up

• Developed societies have progressed through 3 stages that affect age and sex distributions

Epidemiological transition

• Shift in the pattern of morbidity and mortality

  • Prior to causes related primarily to infectious and communicable diseases

  • Growing burden of chronic, degenerative diseases because of population aging

Latency/delayed response to toxic substances

• the time period between initial exposure and a measurable response

  • can be a few seconds to several decades

  • i.e. cancer

Case series

information about patients who share a disease in common is gathered over time

Cross-sectional study

• examines the relationship between disease and other variables of interest as they exist in a defined population at one particular time

  • key is particular time - another way to talk about point prevalence

Ecologic study

Study in which units of analysis populations or groups of people rather than individuals (studying the environment)

Case-control study

subjects who participate are defined by the presence of an outcome of interest

• controlling a variable, like when you give a placebo and actual, related to odds ratio

Cohort study

classifies subjects according to their exposure to a factor of interest and then observes them over time to document occurrence of new cases or other health events (all have something in common)

Experimental study

implemented as an intervention study

• i.e. clinical trial

quasi-experimental trial

aims to estimate the causal relationship between an intervention and its outcomes without using random assignment of participants to groups.

Hill’s Criteria of Causality

• Strength

• Consistency

• Specificity

• Temporality

• Biological gradient

• Plausibility

• Coherence

Strength

a strong association is more likely to be causal

Consistency

finding is replicated in various studies

Specificity

one cause leads to one specific effect

Temporality

cause must precede effect

Biological gradient

dose/response relationship

Plausibility

requires a credible biological mechanism — does it make sense?

Coherence

findings matching with existing knowledge

Toxicology

the study of adverse effects of chemicals on living organisms

Toxicologist

Scientist who investigates in living organisms the adverse effects of chemicals and assesses the probability of their occurrence

Poison

any agent capable of producing a deleterious response in a biological system

Toxic agent

a material or factor that can be harmful to biological systems

• i.e. heat and ionizing/nonionizing radiation, substances derived from biological sources, almost all chemicals

Toxicity

the degree to which something is poisonous

• related to the material’s physical and chemical properties

Toxicant

substances that are manmade or as a result of human activity

• toxic effect may occur directly or indirectly

• i.e. cyanide, methanol

Toxant

substance made by living organisms including reptiles, insects, plants, and microorganisms

• i.e. systemic toxins, target organ toxins

Risk assessment

provides a qualitative or quantitative estimate of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences.

Two types of dose-response curves

• response of an individual to a chemical

• response of a population to a chemical

Threshold

the lowest dose at which a particular response may occur

Key terms to describe length and duration of exposure

• Acute - less than 24h

• Subacute - 1 month or less

• Subchronic - 1-3 months

• Chronic - recurring (greater than 3 months)

Routes of entry

• Ingestion

• Injections into the bloodstream

• Contact with the surface of the skin

• Inhalation

  • Most frequently:

  • GI tract

  • respiratory system

  • skin

Ecological model of population health

Vulnerable subgroups of the population

• elderly

• persons with disabilities and chronic diseases

• pregnant women

• children

Environmental epidemiology

the study of diseases and health conditions (ocurring in the population) that are linked to environmental factors

Significance of Airs, Waters, Places

• written by Hippocrates

• in poorest societies, environmental risks are precipitated by poor food, air, and water quality

Methods of testing for toxicology

Subjects used include:

• volunteers who have had normal or accidental exposure

• animals exposed purposively

• cells derived from human, animal, or plant sources

  • in vitro and in vivio

    • in vitro - in the cell

    • in vivo - not living (petri dish)

Steps in risk assessment

1. Hazard identification

2. Dose-response assessment

3. Exposure assessment

4. Risk characterization

Hazard identification

a hazard is identified as the inherent capability of a natural or human-made agent or process to adversely affect human life, property, or activity, with the potential to cause a DISEASE, EPIDEMIC, ACCIDENT, or DISASTER.

Dose-response assessment

The measurement of the relationship between the amount of exposure and the occurrence of the unwanted effects

Exposure assessment

The procedure that identifies populations exposed to the toxicant describes their composition and size, and examines the roots, magnitudes, frequencies, and durations of such exposures. Includes 3 steps.

3 steps of exposure assessment

1. Characterize the point of exposure, setting, and scenario

2. Identify exposure pathways

3. Quantify the exposure

Risk characterization

Develops estimates of the number of excess unwarranted health events expected at different time intervals at each level of exposure

Environmental risk transition

changes in environmental risks that happen as a consequence of economic development in the less developed regions of the world

• for example, in poorest societies, risks are precipitated by poor food, air, and water quality

New environmental problems develop when above brought under control

• i.e. acid rain precursors, ozone-depleting chemicals, and greenhouse gases.

Exposure dose

External dose

Absorbed dose

Internal dose

Administered dose

Effective dose

Total dose

Measures of disease frequency used in epidemiology include:

• prevalence

• incidence

Prevalence

the number of existing cases of or death from a disease or health condition in a population at some designated time

Incidence

Occurrence of new disease or mortality within a defined period of observation in a specified population

Two classes of epidemiological studies include:

• Descriptive epidemiology

• Analytic epidemiology

Descriptive epidemiology

outline of the occurrence of disease in populations according to classification by person, place, and time variables

• i.e. demographics such as sex, age, ethnicity/race; refers to specific countries; time refers to a year, month, etc

Analytic epidemiology

examines causal hypotheses regarding the association between exposures and health conditions

• i.e. natural experiments - naturally occurring circumstances in which subsets of the population have different levels of exposure to a hypothesized causal factor in a situation resembling an actual experiment

Experimental study

implemented as an intervention study

• i.e. clinical trials

Case series study

information about patients who share a common disease is gathered over time

Cross-sectional study

examines the relationship between disease and other variables of interest as they exist in a defined population at one particular time. Another way to talk about point prevalence.