Environmental Health Investigations: Conducting Environmental Health Assessments.
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Transcript of Environmental Health Investigations: Conducting Environmental Health Assessments.
Goals
Describe the basic steps of conducting an environmental health assessment
Identify when it is appropriate to conduct an environmental health assessment
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
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
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
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
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
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
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.
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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 assessment—may 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
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