Environmental Health Investigations: Conducting Environmental Health Assessments

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Environmental Health InvestigationsConducting
Environmental Health Assessments
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Goals

• Describe the basic steps of conducting an
  environmental health assessment
• Identify when it is appropriate to conduct an
  environmental health assessment

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What is an environmental health assessment?

• A systematic, detailed, science-based evaluation
  of environmental factors that contributed to the
  transmission of a particular disease in an
  outbreak
• It is not a general inspection of operating
  procedures or sanitary conditions like that used
  for licensing
• Focuses on the problem at hand and considers how
  the causative agent, host factors, and
  environmental conditions interacted to result in
  the problem

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Environmental Health Assessment

• Often focuses on a vehicle implicated in an
  outbreak investigation such as
• Contaminated food item
• Cosmetic
• Blood product
• Medicine
• When no specific vehicle has been implicated the
  assessment focuses on the setting where the
  problem occurred

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Environmental Health Assessment Goals

• Identify
• Possible points of contamination with the
  causative agent (ie. microbe or toxin)
• Determine whether the causative agent could have
  survived or not been inactivated
• Determine whether conditions were conducive to
  growth/toxin production by the causative agent

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Contamination

• Introducing or allowing the introduction of
• Pathogenic microorganisms, natural toxins or
  other poisonous substances
• Problem sources may include
• Contaminated raw materials, an infected person,
  cross-contamination or unclean equipment
• Influencing factors
• Breaks in packaging, poor storage practices

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Survival

• Factors may allow survival of pathogenic
  microorganisms or fail to inactivate heat-labile
  toxins
• Factors supporting survival may include
• Inadequate sterilization/heat-processing
• Inadequate reheating
• Inadequate use of preservatives

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Growth

• Factors may allow pathogenic bacteria and fungi
  to multiply or allow toxigenic bacteria and molds
  to elaborate toxins
• Conditions supporting growth include
• Inadequate refrigeration
• Inadequate hot-holding
• Prolonged storage (preservatives break down)
• Anaerobic packaging
• Inadequate fermentation

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Important points to remember Critical Control
Points

• Factors that lead to contamination, survival and
  growth of causative agent may not be sufficient
  to cause a health problem
• Subsequent steps in production/use of the vehicle
  may control the problem by eliminating it or
  reducing it below a critical level.

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Important points to remember Critical Control
Points

• Critical control points steps in the
  preparation of a food item where action can be
  taken to prevent/eliminate a food safety problem
• Example food item contaminated through
  bare-handed contact by infected worker
• If food is not cooked after this contact (ex.
  tuna salad), the pathogen could survive, multiply
  and cause illness
• If the food item is cooked after contact (ex. raw
  chicken), pathogens will likely be destroyed

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Important points to remember Antecedents

• In addition to identifying possible points of
  contamination, survival and growth, identifying
  antecedents is very valuable
• Antecedents circumstances behind the problem
  such as
• Inadequate worker education
• Behavioral risk factors
• Management decisions
• Social and cultural beliefs
• Identifying antecedents allows development of
  effective interventions to prevent future
  occurrences of the problem

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Important points to remember Antecedents

• Example outbreak of salmonellosis linked to
  potato salad Salmonella contamination was from
  chicken thawing above salad ingredients in
  refrigerator
• Important antecedents
• Recent hire of more part-time workers over
  full-time workers
• Part-time workers lacked experience and did not
  make good decisions on foodhandling practices
• Workers not closely supervised
• Correction required
• Education of workers on handling raw chicken AND
  general education on good foodhandling practices
• Ongoing oversight of foodhandling activities by
  experienced person

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Conducting an environmental health assessment

• Sources of information
• Product information
• Written policies or procedures
• Direct observations and measurements
• Interviews with employees and managers
• Lab testing of suspect vehicles, ingredients and
  environmental surfaces
• Lab testing of employees/others in contact with
  suspect vehicles

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Conducting an environmental health assessment

• Specific activities differ depending on causative
  agent, suspect vehicle and setting
• Useful example of typical activities
• Environmental health assessment of a food
  implicated in a foodborne disease outbreak

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Environmental health assessment of food
implicated in an outbreak

• Steps to be undertaken
• Describe the implicated food
• Observe procedures used to make food
• Talk with foodhandlers and managers
• Take measurements
• Collect specimens
• Collect documents on the source of the food

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Describing the implicated item

• Investigator first describes the item by
• Obtaining the recipe (in writing if possible)
• Determining the quantity prepared and sources of
  ingredients
• Considering the intrinsic chemical and physical
  characteristics including
• Expected microbial/toxin content, pH, water
  content, sugar content
• Determining whether the food is likely to allow
  survival and growth of the causative agent

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Observing procedures used to make implicated food

• Investigator observes procedures from receipt of
  raw ingredients to finished product including
• How ingredients were cleaned and stored
• How foods were thawed, cooked, cooled, reheated,
  served and transported
• What equipment was used in preparation and
  condition of the equipment
• Whether the floor design of facility and employee
  traffic patterns would prevent cross-contamination

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Talking with foodhandlers and managers

• Investigator talks with staff familiar with the
  food preparation process and
• Determines the food preparation schedule
• Dates, times and persons involved
• Collects information about the food handlers
• Use of gloves, handwashing, recent illnesses
• Asks about standard operating procedures
• Sick foodhandler policies, food safety education

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Measurements and collecting samples

• Investigator measures
• Time and temperature conditions to which food
  and/or ingredients were exposed
• If not known, measurements may also be taken of
  water activity, sugar content and pH of suspected
  food
• Collecting samples
• Leftovers of implicated food and all its
  ingredients
• Swabs of food preparation surfaces or equipment

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Reviewing records and collecting identifying
information

• Final steps are to collect information which may
  include records such as
• Results of past inspections or complaints
• Worker logs or time cards
• Monitoring cards (e.g. temperatures in walk-in
  refrigerators)
• Investigators may also collect identifying
  information about the implicated food
• Brand name, distributor, batch and lot number,
  dates produced/shipped/received and quantities
  received

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Flow Diagrams

• Investigators often draw a flow diagram to
  summarize information from an environmental
  health assessment
• Flow diagrams show each step in the production
  and use of the vehicle
• Can help verify production activities
• Can help identify possible points of
  contamination or microbial growth and survival

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Sample Flow Diagram
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Who should conduct an environmental health
assessment?

• Investigator needs a good understanding of the
  following factors
• Causative agent
• Factors necessary to cause illness
• Implicated vehicle
• Typically requires someone with special training
  such as a sanitarian or environmental health
  specialist
• May require someone with special
  knowledge/experience of particular causative agent

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Where should an environmental health assessment
be conducted?

• Should take place where the problem leading to
  the outbreak occurred
• Could be where the suspect vehicle was produced,
  processed, stored, used or transported
• Could involve several of these places
• Decision about where to focus the assessment may
  be obvious or may require collection of
  information (ie. traceback investigation) to
  determine where the problem occurred

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When should an environmental health assessment be
conducted?

• Timing depends of specifics of the outbreak
• Early investigation and collection of specimens
  are most revealing
• Important to act as quickly as possible
• Vehicles such as food can be discarded
• Individuals/groups involved in production,
  processing, storage and transportation can change
  practices and procedures as a result of the
  outbreak

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What not to do

• The Burrito Blunder example
• Oct. 1997 Oct. 1998, 16 outbreaks of
  gastrointestinal illness in 7 states
• All but one outbreak occurred in a school
• 1,700 persons affected
• Predominant symptoms were abdominal cramps,
  vomiting, headache and nausea
• No etiologic agent isolated but burritos
  implicated as the source in one outbreak

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The Burrito Blunder continued

• Investigators next steps
• By the time a source was identified, the school
  cafeteria had discarded the leftover burritos and
  garbage pick-up had occurred
• Investigators went to the dump and used a
  forklift to find the burritos under a huge pile
  of other garbage
• Burritos were not in good shape and investigators
  were unable to identify a causative agent

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When should an environmental health assessment be
conducted?

• If you have no clues on a source, it is difficult
  (and wasteful) to initiate an environmental
  health assessmentmay need to wait until
• A causative agent is isolated
• Results from epidemiologic studies or
  hypothesis-generating interviews are available
• Analytic epidemiologic studies have implicated a
  specific vehicle

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Conclusion

• Environmental health assessments provide valuable
  insights into an outbreak
• Identify breakdowns in techniques, system design
  and/or operation, or human error
• Allow you to identify points where you can
  intervene to stop the problem and prevent future
  occurrences
• Combining information from epidemiologic,
  laboratory, and environmental health studies puts
  the characteristics of the agent, host and
  environment together
• Control measures can therefore be implemented
  more quickly and they are more likely to be
  effective

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References

• 1. CDC. Outbreaks of gastrointestinal illness of
  unknown etiology associated with eating
  burritosUnited States, October 1997-October
  1998. MMWR Morb Mortal Wkly Rep. 199948210-213.