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What are the 4 factors in the cycle of microbial disease?

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What are the 4 factors in the cycle of microbial disease?

  • factor 1 - reservoir

  • factor 2 - modes of transportation; 4 basic conditions must be met for disease transmission to occur

  • factor 3 - portals of entry

  • factor 4 - portal of exit

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What is factor 1 - reservoir?

site or place in nature in which the microbe survives and even multiples

  • could be non living (soil, water) or living ( animals)

  • target for preventing, minimizing, and eliminating the disease

  • domestic and wild animals serve as the reservoirs for about 150 pathogens that affect humans

  • humans are the only known reservoirs for smallpox, gonorrhea, measles, and polio

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What is factor 2 - modes of transportation? *four basic conditions must be met for disease transmission to occur

  • condition 1 - viable pathogen must be present

  • condition 2 - viable pathogen must be present in an infective dose

  • condition 3 - host must be available

  • condition 4 - a means must be present for the pathogen to enter the host

*if any of the conditions is not met, transmission cannot occur and a public health risk infection is not present

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In factor 2 - modes of transportation, what are the different types of transmission?

  • direct transmission (horizontal, droplet) - person-to-person contact; immediately transferred from portal of exit to portal of entry (animal bites)

  • direct transmission (vertical) - pathogen passed from mother to offspring via placenta (AIDS, measles, chickenpox), breast milk, birth canal (syphilis, gonorrhea)

  • indirect transmission - passage of pathogen from a reservoir to an intermediate agent then the host; intermediate agent could be living or nonliving (fomite: food, water, blood; toothbrush, comb, contact lenses, cell phones, ATM, TV remote)

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What is factor 3 - portals of entry?

routes by which a pathogen gains access to the host

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What is factor 4 - portal of exit?

routes by which a pathogen leaves the host

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In the control of epidemics, how do you reduce or eliminate the reservoir?

  • quarantine / isolation or carriers

  • destruction of animal reservoirs

  • treatment of sewage

  • therapy to reduce the infectivity of infected individuals

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In the control of epidemics, how do you break the connection (route of transmission) between source and susceptible individuals?

  • chlorination of water supplies

  • pasteurization of milk

  • inspection of food and food handlers

  • use of pesticides to destroy vectors

*via sanitation, disinfection, vector control, etc.

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True of False: Understanding and controlling factor 2 is the primary way to break the cycle of disease


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caused by natural cosmotelluric phenomena (eclipses, comets, earthquakes)

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caused by noxious vapors and smells; bad air or swamp air

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caused by non-living decomposed animal; organic substances introduced into new hosts

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Scientific study that evaluates the occurrence, determinants, distribution, frequency and control of health and disease in a defines (typically human) population.

  • data driven and relies on a systematic and unbiased approach to the collection, analysis, and interpretation of data

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Systematic epidemiology

branch of epidemiology concerned with the ecological and societal factors that influence the development and emergence of disease

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What are the 5 Ws?

what - diagnosis or health event

who - person

where - place

when - time

why/how - causes, risk factors, modes of transmission

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Morbidity (Rate)

Number of cases of illness per 100,000 people per year

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disease co-occurrence; simultaneous presence of two or more chronic diseases or conditions in a patient

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Mortality (Rate)

number of deaths per 100,000 people per year

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Index case

the first case identified in an epidemic

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the study of the causes of disease

  • “what is the etiologic agent?”

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branch of medicine that deals with the classification of disease

  • disease may be classified by etiology, pathogenesis, symptomology, or affected organ systems

  • used for public health and epidemiological studies

    • death certificates requires nosological coding as for the cause for death

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a disease of unknown or spontaneous origin

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What is Prodromal (stage)? What is meant by sign, symptom, and syndrome?

the onset signs and symptoms without any clarity of diagnosis

  • sign → objective change or manifestation in the body (fever, rash) that can be directly observed

  • symptom → subjective change or complaint (pain, appetite loss, dizziness) experienced by the patient

  • syndrome → compilation of signs and symptoms that is characteristic of a specific disease state

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the origin and description of how the disease process evolves

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the study of physiology that has been altered by disease

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the aggregation of two or more diseases in a population

  • typically develops under conditions of health disparity caused by poverty and disease

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Herd Immunity (or Community Immunity)

epi theory that describes a form of immunological protection that occurs when a significant portion of the population is vaccinated, or been previously exposed to a contagious disease which then provides some measure of protection for those individuals who has not developed immunity

  • theorizes that larger groups of individuals that are less susceptible to the disease can disrupt the chain of infection

  • on the other hand, if too few people are vaccinated, herd immunity then fails to protect the overall populations

  • ex: measles

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Herd Immunity hypothesis

  • claims to indirectly disrupt chain of infection

  • ethically flawed - there is risk of death in young people, though less than others

  • operationally flawed - if elderly and debilitated were quarantined who would take care of them

  • scientifically flawed - never seen herd immunity generate to any other infection; influenza occurs every year, TB and malaria continues

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T or F: breakthrough infections elude herd immunity


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Area Postrema

name of the sensory organ in the brain (medulla) that controls vomiting

  • plays a role in the control of autonomic (involuntary) functions of the CNS

  • circumventricular organ (CVO) with extensive vasculature which bypasses the blood brain barrier (BBB)

  • therefore, allows for linkage between the CNS and peripheral blood flow which provides a route for peptides and hormones to target neural tissue

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T or F: It has be hypothesized that chemical signals, from both pathogenic and beneficial microorganisms, interact with the microvilli of the small intestine and carry electrical impulses up the vagus nerve and into brain structures responsible for emotions like anxiety


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Disease reproduction number (Ro) Model in epidemiology

tool used to measure the transmission potential of a disease

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Ro/R-zero/basic reduction number/basic reproduction ratio

number of new infections that would result from the introduction of a single infectious individual into an entirely susceptible population of the same species

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Ro < 1

  • disease dies out

    • means that 1 infectious individual would generate, on average, less than 1 new infection

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Ro > 1

  • disease outbreak

    • infectious individual would generate, on average, more than 1 new infection and disease outbreak would occur

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What could the Ro be affected by?

  • duration of the infectivity of affected patients

  • infectiousness of the infectious agent

  • infectious dose needed to make a person sick

  • number of susceptible people in the population that the affected patient are in contact with

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The simplest epidemiological model to help explain spread of infections is called SIR. What does it stand for?

  • S - susceptible

  • I - infectious

  • R - recovered

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What is the equation for Ro value?

Ro = t x c x d

  • t = transmissibility

  • c = contact

  • d = duration

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What is covid Ro value?


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What is the Ro value for HIV, Hepatitis C, and Ebola?

  • HIV 2-4

  • Hepatitis C 2-4

  • Ebola 1.5-2

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Other examples of Ro value

knowt flashcard image
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What is the #1 bacterial food borne illness?


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T or F: # 1 cause of food borne illnesses are bacteria, followed by viruses

FALSE: # 1 cause of food borne illnesses are viruses, followed by bacteria

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Why is food borne illness surveillance so complicated?

  • it is frequently not reported

  • transmission is also via water, ice, person to person (fecal oral route)

  • certain unknown percent caused by agents still not identified

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Food poisoning

occurs when food that looks normal, smells normal, and tastes normal is eaten - enough is eaten to make you ill from the ingested pathogens or toxins

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Food spoilage

does not usually cause food poisoning or illness because the consumer usually rejects the food before ingestion

  • is a way that nature alerts our senses to reject eating the food which in turn prevents illness and maintains health

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  • based on olfactory - would determine the quality of the seafood (fresh or decomposed)

  • food high in nitrogen smells

  • sensory exam - smell, touch, sight; NO tasting

  • class 1 - good, class 2 - middle, class 3 - bad

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What is an emerging disease?

infectious disease whose incidence is increasing following its first introduction into a new host population

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What is a re-emerging disease?

one whose incidence is increasing in an existing host population as a result of long term changes in its underlying epidemiology

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Most emerging diseases are _______


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What are the main contributors to emerging diseases?

  • world population growth (population overload) - 80% of population lives in less developed areas; population density

  • urbanization

  • ecological disturbances, environmental disruption, disintegration of natural ecosystems, deforestation, climate change, changes in land use, natural disasters

  • technological advances / industrial advances - jet travel, food processing, livestock handling, international travel and commerce

  • human factors - migration, war, sexual behavior, drug use

  • microbal changes - antibiotic resistance, mutations

  • breakdown of public health measures - sanitation, vaxx, insect and pest control

  • globalization - diverse food supply (#1 concern)

  • outdated laws and insufficient strategic planning

  • lack of resources

  • inadequate coordination across multiple agencies and jurisdictions (federal, foreign, state, local)

  • changing consumption patterns (greater than 50% of food dollars spent outside the home)

  • shifting demographics (aging population, cancer, diabetes, obesity, etc)

  • intentional adulteration, especially post 9/11 (food safety vs. food defense /security)

  • growing industrialization causing larger and wide-spread outbreaks

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T or F: the food safety system includes producers, processers, shippers, retailers, food preparers, and ultimately the consumers; it is complex and multi-level, essentially uncoordinated and fragmented


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  • DHHS → department of health and human services

  • FDA → food and drug administration (within DHHS)

    • regulates the processing, manufacturing, and sale of all domestic and imported foods sold in interstate commerce including shell eggs, with the exception of meat and poultry

    • products with <3% red meat and products with <2% poultry are regulated by FDA - FDA regulates all fish except catfish which is regulated by USDA

      • bottled water, wine beverages containing <7% alcohol, all closed faced sandwiches (e.g. two pieces of bread or a roll enclosing a filling)

        • FDA regulates 80% of US food supply by don’t receive a lot of money

        • 25-30% of our expenses is spent on something the FDA regulates

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  • USDA → U.S. Department of Agriculture

  • FSIS → food safety inspection service (within the USDA)

    • regulates “traditional” domestic and imported meat and poultry (FDA regulates game meats, such as venison, ostrich, snake, rabbit), processed eggs (liquid, frozen, and dehydrated), only catfish, all, open face sandwiches

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Dual Jurisdiction (both FDA and USDA)

pepperoni pizza, sausage (USDA - sausage meat, FDA - sausage casing)

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  • CDC within DHHS

  • all foods, investigates with local, state, and other federal officials food borne outbreaks, directs and enforces quarantines

    • surveillance and response:; applied research ; infrastructure and training; prevention and control

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  • Public Health Service within DHHS

  • headed by the US surgeon general; which originally concerned with the health care of sailors

  • provides help to other agencies (hurricane katrina, gulf oil spill, etc)

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  • responsible for the oversight for drinking water, foods made form plants, seafood, meat, and poultry

  • establish the safety and tolerance levels of pesticide residues in foods (pesticide on oranges); determines the registration of pesticides; establishes water quality standards for potable water

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  • FTC → Federal Trade Commission

    • regulates deceptive and unsubstantiated advertising of all foods

      • can’t claim “prevents heart diseases” unless data is shown

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  • within the department of commerce

  • inspects and certifies fishing vessels, seafood processing plants and retail facilities for federal sanitation standards

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  • national marines fishery service

  • within the department of commerce - a division of NOAA

  • responsible for the enforcement of seafood quality (non-microbiological) and identification; aquaculture management and production

    • works closely with the states and the US Coast Guard and FDA

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  • alcohol and tobacco tax and trade bureau (within the department of treasury)

  • enforces food safety governing the production, distribution and labeling of alcoholic beverages

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U.S. Customs

  • all imported foods

    • now part of the department of homeland security; once part of the department of treasury

    • major with the FDA and USDA

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prosecutes companies and individuals, seizes adulterated products

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  • NIH → national institute of health

  • nation’s medical research within DHHS

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What are the major responsibilities of state health departments?

establish and implement safety regulations pertaining to food and water sanitation (use of gloves, protective shields over salad bars)

  • control of the milk industry with each state

  • inspects restaurants, grocery stores and food manufacturing plants within local jurisdiction

  • surveillance and control of infectious disease

  • embargo unsafe foods made or distributed within the state

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T or F: Each state can and does formulate their own laws to represent their local needs


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  • world health organization

  • promote global health; watchdog for outbreaks of infectious disease

    • influenza, SARS, malaria, tuberculosis, AIDS, polio, smallpox

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  • food and agriculture organization

  • role in public health hazard with foods

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Codex Alimentarius (latin - food book)

  • food and agriculture organization

  • established by WHO as a collection of internationally recognized standards, codes of practice, guidelines and recommendations relating to foods, food production and food safety to promote consumers’ health and facilitate fair practices in international trade

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What is the Federal Register? What does it contain?

  • daily newspaper of the federal government

  • to inform citizens of their rights and obligations and provide access to a wide range of federal benefits and opportunities for funding

    • published every business day by the national archives and records administration

  • it contains:

    • federal agency regulations

    • proposed rules and public notices

    • executive orders

    • proclamations

    • other presidential documents

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Why would you need to read/use the Federal Register?

  • you need to now about day to day operations of the federal government

  • your business is regulated by federal agency

  • you are an attorney practicing before a regulatory agency

  • your organization attends public hearings or meetings or applies for grants

  • you are concerned with government actions that affect the environment, healthcare, financial services, exports, education, or other major policy issues

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United States v. Dotterweich (1943)

  • Buffalo Pharmacal Co purchased drugs from a manufacturer, repackaged them, and shipped them with a new label

  • supreme court ruled that the responsible officials of a corporation, as well as the corporation itself may be criminally prosecuted for violations of the FDC Act

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United States v. Park (1975)

  • defendant Mr. Park, president of Acme grocery store chain was individually convicted of causing the adulteration of various foods

  • supreme court held that the defendant need not have personally participated in the situation that caused the alleged adulteration, but that the defendant “had a responsible relation to the situation” and that virtue of his position Mr. Park had the “authority and responsibility” to deal with such conditions that led to adulteration

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United States v. Dotterweich (1943) AND United States v. Park (1975) UPHOLDS THAT _____ + ______ = ____________


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Stewart Parnell & Peanut Corp. of America (PCA) (2015)

  • deadly salmonella outbreak involving shipping contaminated peanut products nationwide

    • leaky roof - bird poop from roof - salmonella in peanut butter

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Risk definition

a function of likelihood and severity; implies probability that harm, injury, disease or death will occur

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T or F: The estimation (likelihood and severity) or risk is a scientific question (factual) whereas the acceptability of a given level of risk is a political question (value)


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What is risk management (rm)?

  • managerial approach that makes sure what we are doing is the right thing; what we decided to implement makes sense to control risk

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What is quality management system (qms)?

  • critical role to make sure we are doing it right (monitors and verifies what RM decided to implement is actually working and effective in controlling the risk, if not, QMS is responsible to alert RM to modify what is being done

  • typically RM and QMS should be working together in a coordinated fashion as a team

  • QMS serves as a check on RM

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what factors are important in a risk assessment (or hazard analysis) which all relate to the infectious agent?

  • pathogenicity of the infectious agent (mild morbidity versus high mortality)

  • route of transmission (airborne, parenteral, ingestion)

  • infectious dose

  • stability of the infectious agent (ability to survive over time in the environment)

  • origin (geographic location, host, etc.)

  • availability of the therapeutic intervention (vaccine, antibiotic, etc)

  • susceptibility of the population to the infectious agent

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as a general rule, people tend to _____ risk if they are unfamiliar, hard to understand, invisible, involuntary, and catastrophic - whereas people tend to ______ risk if they are clear and comprehensive

  • overestimate

  • underestimate

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What is market withdrawal?

when a product has a minor violation that would not be subject to FDA legal action - the company removes the product from the market or corrects the violation

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What is recall?

actions taken by a firm to remove a product form the market

  • recalls may be conducted on a firm’s own initiative, by FDA request, or by FDA order under statutory authority

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What are the 3 kinds of recall classifications?

  • class 1 - there is a reasonable probability that the use of exposure to a violative product will cause serious adverse consequences or death (e. coli 0157:H7)

  • class 2 - use of exposure to a violative product may cause temporary or medically reversible adverse health consequences, or the probability of serious adverse health consequences is remote

  • class 3 - use of or exposure to a violative product is not likely to cause adverse health consequences

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What is an import alert?

  • FDA’s way of telling the world that the Agency think you products present safety problems

  • as a result of an import result, FDA will automatically detain your products at the border, costing customers a lot of money

  • issued whenever FDA determines that it already has sufficient evidence to conclude that your products appear to be adulterated, misbranded, or unapproved, and that therefore they may be refused admission.

  • i the FDA refuses the shipment because the importer decides not to bother trying to reverse an FDA automatic detention, or because the importer decides not to bother trying to reverse an FDA automatic detention, or because the importer or private lab or customs broker fails to meet a simple deadline, the refused shipment will have to be exported or destroyed

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What did 16th century alchemist Paracelsus (father of toxicology) say?

“Poison in everything, and nothing is without poison. Therefore the dosage makes it either a poison or a remedy.”

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There is an interplay of legislative, regulatory, scientific, social and political forces with every food safety issue. The food industry also plays a critical role. Some food safety issues include the following:

  • environment contaminants (heavy metals, pesticide residues

  • product tampering

  • nutritional quality

  • microbial contamination

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safety explain to congress, should be understood not in _________ terms but as a demonstration to a ______________ that no harm will result from consumption of the substance under intended conditions of use

absolute; “resonable certainty”

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Adulteration definition and examples

  • if it bears or contains any poisonous or deleterious substance which may render it injurious to health; if it bears or contains any added poisonous or added deleterious…; if it consists in whole or in part of any filthy, putrid or decomposed substance, or if it is otherwise unfit for food…

  • ex: bread with chalk; pepper with juniper seeds; milk with water; orange juice with beet and/or corn syrup; olive oil with canola oil; honey with corn syrup…

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Dr. Harvey Wiley became chief chemist of the US Bureau of Chemistry (then part of USDA)

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What is the “poison squad”?

a group of volunteers who consumed questionable food additives

  • campaigned for a national food and drug law and helped galvanized public awareness and advanced food safety

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publication of The Jungle by Upton Sinclair portraying the unsanitary practices in the meat packing industry in Chicago - final catalyst for change

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President Theodore Roosevelt signed Pure Food and Drug Act and the Meat Inspection Act thus beginning modern era of US food regulation

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sulfanilamide was being used effectively to treat strep throat and other bacterial diseases

  • in order to increase palatability, a drug company mixed it with antifreeze which has a sweet pleasant taste

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  • food drug and cosmetic act was enacted in response to the sulfanilamide tragedy - made improvements to 1906 act:

    • required premarket approval and proof of the safety of drugs

    • extended government control to cosmetics and therapeutic devices

    • provided safe tolerance levels be set for unavoidable poisonous substances in food

    • authorized standards of identity, quality, and container fill for foods

    • authorized factory inspections

    • added court injunctions to the previous penalties of seizures and prosecutions

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  • food additives amendment - requiring evaluation of food additives to establish safety

  • Delaney clause forbade the use of any substance in food that was found to cause cancer in laboratory animals

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What is a low acid food?

pH >4.6

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Color additive amendment required manufacturers to establish the safety of color additives to foods, drugs, and cosmetics

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Low-Acid Food Processing Regulations is issued by FDA after publicized outbreaks of botulism from canned foods

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