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 – 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 MMWR Morb Mortal Wkly Rep. 1999;48: