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

Sample Flow Diagram

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

References

1. CDC. Outbreaks of gastrointestinal illness of unknown etiology associated with eating burritos—United States, October 1997-October 1998. MMWR Morb Mortal Wkly Rep. 1999;48:210-213.