Title: Environmental Health Investigations: Conducting Environmental Health Assessments
1Environmental Health InvestigationsConducting
Environmental Health Assessments
2Goals
- Describe the basic steps of conducting an
environmental health assessment - Identify when it is appropriate to conduct an
environmental health assessment
3What 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
4Environmental 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
5Environmental 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
6Contamination
- 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
7Survival
- 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
8Growth
- 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
9Important 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.
10Important 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
11Important 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
12Important 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
13Conducting 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
14Conducting 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
15Environmental 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
16Describing 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
17Observing 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
18Talking 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
19Measurements 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
20Reviewing 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
21Flow 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
22Sample Flow Diagram
23Who 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
24Where 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
25When 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
26What 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
27The 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
28When 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
29Conclusion
- 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
30References
- 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.