Environmental Health Investigations: Conducting Environmental Health Assessments

VOLUME 3, ISSUE 4

Imagine that you’re whipping up a the transmission of a particular dis- batch of your famous chocolate chip ease in an outbreak. An environ- CONTRIBUTORS cookies. As you take them steaming mental health assessment is not a hot out of the oven, you can’t help general inspection of operating proce- Authors: but sample one…. Ugh! They just dures or sanitary conditions like that Jeanette K. Stehr-Green, MD don’t taste right! What’s wrong with used for licensing an assisted living those cookies? As you go back over facility or a restaurant. Rather, an Paul A. Stehr-Green, DrPH, MPH every step, every ingredient, and environmental health assessment Amy Nelson, PhD, MPH every measurement, you discover focuses on the problem at hand and Reviewers: your mistake. You added salt in- considers how the causative agent, stead of sugar! host factors, and environmental condi- FOCUS Workgroup* tions interacted to result in the prob- In the same way that you went back Production Editors: lem. over every step to find the source of Tara P. Rybka, MPH your cooking mishap, an environ- The environmental health assessment Lorraine Alexander, DrPH mental health assessment goes often focuses on a vehicle implicated Rachel A. Wilfert, MD, MPH back over events to help to identify in an outbreak investigation such as a the possible cause of an outbreak. contaminated food item, cosmetic, Editor in chief: blood product, or medicine. In some In the last issue of FOCUS, we ex- Pia D.M. MacDonald, PhD, MPH instances, when a specific vehicle has plored traceback investigations. not been implicated, the assessment Tracebacks are used to find the focuses on the setting in which the point at which an item implicated in problem occurred or is thought to an outbreak may have become con- * All members of the FOCUS have occurred. For example, the inves- taminated. Remember that a trace- Workgroup are named on the last tigation might focus on the kitchen in back does not identify the source of page of this issue. which a meal associated with a food- the problem; it just tells investigators borne disease outbreak was prepared where to look. or an operating room that was linked Once you’ve identified where the to an increased risk of surgical wound contamination occurred, the environ- infections. The goals of an environmental health assessment is neces- mental health assessment are to iden- sary to identify the practices or con- tify: ditions that may have resulted in the • possible points of contamination problem and to implement control with the causative agent (i.e., a measures to prevent the problem microbe or toxin); from happening again. • determine whether the causative agent could have survived or not What is an Environmental Health been inactivated; and Assessment? The North Carolina Center for Public Health • determine whether the conditions Preparedness is funded by Grant/Cooperative Agreement Number U90/CCU424255 from the Centers An environmental health assess- were conducive to subsequent for Disease Control and Prevention. The contents of this ment is a systematic, detailed, sci- growth or toxin production by the publication are solely the responsibility of the authors and do not necessarily represent the views of the CDC. ence-based evaluation of environ- causative agent. mental factors that contributed to

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FOCUS ON FIELD EPIDEMIOLOGY Page 2

“Contamination” involves factors that introduce or permit Second, although the primary goals of an environmental the introduction of pathogenic microorganisms, natural health assessment are to identify possible points of con- toxins, or other poisonous substances. Sources of the tamination, survival, and growth, to be most valuable, the problem may include contaminated raw materials, an in- investigation needs to identify “antecedents” that resulted fected person, cross-contamination from another contami- in these conditions. “Antecedents” are the circumstances nated item, and unclean equipment. Factors influencing behind the problem. They include things like inadequate contamination include breaks in packaging and poor stor- worker education, behavioral risk factors, management age practices. decisions, and social and cultural beliefs. Only by identifying the problem behind the problem will investigators be “Survival” involves factors that allow the survival of patho- able to develop effective interventions to prevent future genic microorganisms or fail to inactivate heat-labile toxins occurrences of the problem. already present. Factors supporting survival include inadequate sterilization or heat-processing of an item, in- Here is a fairly typical example: An outbreak of salmonel- adequate reheating, or inadequate use of preservatives. losis in a small community was linked to potato salad served at a local restaurant. The environmental health “Growth” involves factors that allow pathogenic bacteria assessment determined that the potato salad was proba- and fungi present to multiply to numbers sufficient to bly contaminated with Salmonella from chicken that was cause illness or allow toxigenic bacteria and molds to thawing above the potato salad ingredients in the refrig- elaborate toxins. (Note: viruses and parasites do not repli- erator. cate in vehicles but require hosts to “grow.”) Conditions that support growth include inadequate refrigeration, in- The root of the problem, however, was deeper. To save adequate hot-holding, prolonged storage (so that preserva- money, the manager had begun hiring more part-time tives break down and are no longer active), anaerobic workers (whom he could pay less) rather than full-time packaging, and inadequate fermentation. employees (to whom he would have to provide benefits). Although the part-time workers had taken a food safety There are two important points to remember. course from the local health department, they lacked ex- First, the presence of factors that lead to contamination, perience and did not always make good decisions on food- survival, and growth of the causative agent may not be handling practices. And the workers were not closely su- sufficient to cause a health problem. If subsequent steps pervised. So correcting the problem required not only edu- in the production and/or use of the vehicle control the cation of the workers on the proper handling of raw problem introduced by the factor (i.e., eliminate it or re- chicken but general education on good food handling tech- duce it below a critical level), the factor will no longer cre- niques and ongoing oversight of the foodhandling activi- ate a problem. Let’s use the example of contamination of ties by a knowledgeable and experienced person. a food item through bare-handed contact by an infected food worker to illustrate this point. How Should the Environmental Health Assessment Be • If the food is not cooked after this contact (let’s say it Conducted? is tuna salad), the bare-handed contact may cause a Sources of information for an environmental health as- problem. The pathogen could survive and multiply sessment include product information (e.g., chemical and sufficiently to cause illness in someone who con- physical characteristics and source); written policies or sumes the food. procedures; direct observations and measurements; interviews with employees and managers; and lab testing of • If the food item is cooked after contact (let’s say it is suspect vehicles, ingredients, and environmental surfaces. raw chicken), the bare-handed contact will probably not be a problem. Proper cooking will destroy patho- Sources of Information gens introduced into the food. for an Environmental Health Assessment • This is referred to as a “critical control point” in the • Product information food safety world. Critical control points are steps in • Written policies and procedures the preparation of a food item where action can be • Direct observations and measurements taken to prevent or eliminate a food safety problem. • Interviews with employees and managers Control of the problem at the critical control point is necessary because it will not be addressed in subse- • Lab testing of suspect vehicles, ingredients, or quent steps in the preparation of the food. environmental surfaces • Lab testing of employees or others in contact with the suspect vehicle or environment

North Carolina Center for Public Health Preparedness—The North Carolina Institute for Public Health

VOLUME 3, ISSUE 4 Page 3

On occasion, clinical specimens may be collected from between food preparation activities to prevent cross- people in contact with the suspect vehicle (e.g., foodhan- contamination. dlers, factory-line workers) or the environment in which it The investigator talks with foodhandlers and managers was produced or used. familiar with the food preparation process and facility. He The specific activities included in an environmental health or she determines the food preparation schedule assessment differ depending on the causative agent, the (including the date and time of preparation) and the per- suspect vehicle, and the setting. Let’s use the environ- son(s) who prepared the implicated food. The investigator mental health assessment of a food implicated in a food- also collects information about the foodhandlers them- borne disease outbreak as an example of the kind of ac- selves, including use of gloves, handwashing practices, tivities that might be undertaken. and recent illnesses. The investigator also asks about standard operating procedures, including sick foodhandler Environmental Health Assessment policies and routine food safety education of employees. of Food Implicated in Outbreak The investigator • Describe the implicated food measures the • Observe procedures used to make food time and tempera- • Talk with foodhandlers and managers ture conditions to • Take measurements which the food • Collect specimens and/or its ingredi- • Collect documents on the source of the ents were ex- food posed during storage and preparation. The investi- In the environmental health assessment of a food item, gator tries to de- the investigator first describes the implicated item and termine the obtains the recipe for the item, in writing if possible. He or weight/volume of Centers for Disease Control and Prevention she determines the quantity prepared and sources of the food prepared and ingredients. The investigator then considers the intrinsic the depth of containers used to store the food. If not al- chemical and physical characteristics of the food ready known, he or she may also measure water activity, (including the expected microbial/toxin content, pH, water sugar content, and pH of the suspect food to determine if content, and sugar content) and determines whether the the causative agent could survive/grow in the food. food is likely to allow survival and growth of the causative The investigator then collects leftover samples of the impli- agent. cated food and all its ingredients, and where appropriate, The investigator then observes the procedures used to swabs food preparation surfaces or equipment for cultures make the implicated food. This includes all steps from or other tests. receipt of raw ingredients to finished product. The investi- Finally, the investigator reviews the available records and gator examines how the ingredients were cleaned and collects identifying information about the implicated item stored. He or she observes how foods were thawed, and its ingredients. Available records may include the re- cooked, cooled, reheated, served, and transported. The sults of past inspections or complaints, worker logs or time investigator determines what equipment was used in the cards, and monitoring logs (e.g., temperatures in walk-in preparation of the suspect food and the condition of that refrigerators). Identifying information about the implicated equipment. food item will include brand name; producer; distributor; The investiga- batch and lot number; dates produced, shipped, and re- tor considers ceived; and quantities received. This information is col- the floor de- lected to determine the exact source of the food item (and sign of the fa- to facilitate traceback of the item, if appropriate). cility and em- ployee traffic The activities described above are very specific to a food patterns, and item implicated in an outbreak, but you can easily see how determines many of the same activities might be used in the investiga- whether there tion of non-food vehicles. For example, think about the was adequate environmental health assessment for an intravenous separation medicine implicated in an outbreak of sepsis at a hospital.

Centers for Disease Control and Prevention

North Carolina Center for Public Health Preparedness—The North Carolina Institute for Public Health

FOCUS ON FIELD EPIDEMIOLOGY Page 4

What steps might you go through to explore where/how the Who Should Conduct an Environmental Health Assess- problem occurred? What product information would you ment? collect? What activities would you observe? With whom To recognize opportunities for contamination, survival, and would you talk? What records would you examine? growth in an environmental health assessment, the inves- To summarize information gained through an environ- tigator needs a good understanding of: mental health assessment, investigators often draw a flow diagram showing each step in the production and use of • the causative agent (e.g., likely sources, optimum the vehicle. Flow diagrams clearly display the flow of op- growth conditions, inhibitory substances, means of erations, and they can be used to verify production activi- inactivation); ties as different workers/managers are consulted. They • factors necessary to cause illness (e.g., infectious can also help identify possible points of contamination or dose, portal of entry); and microbial survival and growth. • the implicated vehicle (e.g., physical and chemical In these flow diagrams, each operation is represented by a characteristics of the vehicle that might facilitate or rectangle. (NOTE: an “operation” is very narrowly defined. inhibit growth, methods of production, processing, and As you can see in this example on making potato salad, preparation). each operation is like one step in a very detailed recipe.) Arrows indicate the direction of flow of the process. The With a good grasp of this information the investigator can investigator notes other important information directly on home in on the likely source of the problem and the ways the diagram, including measurements (e.g., temperature, in which the causative agent, host factors, and environ- duration of operation) and the name of the person(s) per- mental conditions interacted. The volume of knowledge forming the operation. needed typically requires someone with special training in this field of investigation, such as a sanitarian or environmental health specialist. Circumstances may also require consultation with a person who has special knowledge of or experience with a particular causative agent or vehicle.

Centers for Disease Control and Prevention

North Carolina Center for Public Health Preparedness—The North Carolina Institute for Public Health

VOLUME 3, ISSUE 4 Page 5

Where Should an Environmental Health Example: The Burrito Blunder Glossary Assessment be Conducted? From October 1997 through October An environmental health assessment 1998, 16 outbreaks of gastrointestinal Contamination: The should take place where the problem lead- illness occurred in Florida, Georgia, Illi- introduction of ing to the outbreak (or other health prob- nois, Indiana, Kansas, North Dakota, and pathogenic lem) occurred. This might be where the Pennsylvania. All but one outbreak oc- microorganisms, natural suspect vehicle was produced, processed, curred in a school, and approximately toxins, or other stored, or used or the means by which it 1,700 persons were affected. The pre- poisonous substances. was transported. The investigation may dominant symptoms were abdominal need to focus on several of these places. cramps (88%), vomiting (62%), headache (62%), and nausea (39%), with a short The decision about where to focus the as- incubation period. An etiologic agent was Critical control point: sessment will be based largely on clues to not isolated. Epidemiologic investigations Step in the preparation where the source of the problem lies. This implicated burritos as the source. How- of a food item where may be obvious from information available ever, by the time the investigators had action can be taken to at the outset of the outbreak investigation. pinpointed the likely source in one out- prevent or eliminate a For instance, if an outbreak is associated break, the school cafeteria had discarded food safety problem that with a meal served at a banquet, the as- the leftover burritos and garbage pick-up will not be addressed in sessment is likely to be conducted in the had already occurred. Anxious to identify a later step in the kitchen in which the meal was prepared. the causative agent, investigators scurried preparation of the item. But if the outbreak involves cases across a down to the dump. They used a forklift to state or country (or across the globe), it find the burritos under a huge pile of gar- might not be so clear where to start. Inves- bage. And as you can imagine, the burri- Growth: Pathogenic tigators may need to collect information to tos were not in very good shape. (By the bacteria and fungi determine where the problem most proba- way, to this day, they have not determined present multiply to bly occurred. This usually takes the form of the cause of the burrito-associated risk numbers sufficient to a traceback investigation, as discussed in factor.) (1) cause illness or toxigenic the last issue. bacteria, or molds Of course, if you have no clues on the produce toxins. source, it is very difficult (and even waste- When Should the Environmental Health ful) to initiate an environmental health Assessment be Conducted? assessment. So you may need to wait Survival: Pathogenic until the causative agent has been iso- The timing of an environmental health as- microorganisms are not lated, results from descriptive epidemi- killed, or heat-labile sessment depends on the specifics of the ologic studies or hypothesis-generating outbreak and the information available. toxins already present interviews are available, or analytic epide- are not inactivated. Early investigation and early collection of miologic studies have implicated a spe- specimens are most likely to uncover the cific vehicle. conditions at the time of the outbreak and Centers for Disease Control indicate where things went wrong. In situa- tions where cases are clearly associated Conclusion with a particular meal or setting, environmental studies can be initiated quickly Environmental health assessments provide invaluable insights into an (even before a specific food is implicated outbreak by identifying breakdowns in techniques, system design and/or through an epidemiologic study). In fact, it operation, or just plain “human error” that led to the problem underlying is important to act as quickly as possible! the outbreak. An environmental health assessment allows you to identify Vehicles such as foods can be discarded or points where you can intervene to stop the problem and prevent future grow old. Individuals/groups involved in occurrences. Combining the information from epidemiologic, laboratory, the production, processing, storage, trans- and environmental health studies helps us complete the picture of an portation, or preparation of an item can outbreak or other public health problem by putting the characteristics of change their practices and procedures, the agent, host, and environment together. With this picture, control becoming more conscious about their ac- measures can be implemented more quickly and they are more likely to tivities as a result of the outbreak. be effective. And that’s a good thing!

North Carolina Center for Public Health Preparedness—The North Carolina Institute for Public Health

CONTACT US: REFERENCES: 1. CDC. Outbreaks of gastrointestinal illness of unknown etiology associ- The North Carolina Center for Public Health Preparedness ated with eating burritos—United States, October 1997-October 1998. The University of North Carolina at Chapel Hill MMWR Morb Mortal Wkly Rep. 1999;48:210-213. Campus Box 8165 Chapel Hill, NC 27599-8165

Phone: 919-843-5561 Fax: 919-843-5563 Email: [email protected]

FOCUS Workgroup:

• Lorraine Alexander, DrPH • Meredith Anderson, MPH • David Bergmire-Sweat, MPH • Kim Brunette, MPH • Anjum Hajat, MPH • Pia D.M. MacDonald, PhD, MPH • Gloria C. Mejia, DDS, MPH • Amy Nelson, PhD, MPH • Tara P. Rybka, MPH • Rachel A. Wilfert, MD, MPH

If you would like to receive electronic copies of FOCUS on Field UPCOMING TOPICS! Epidemiology, please fill out the form below: • NAME: ______• Basics of Data Analysis: Variables & Distribution • DEGREE (S): ______• Data Analysis: Simple • AFFILIATION: ______Statistical Tests • E-MAIL ADDRESS: ______• Advanced Data Analysis: • May we e-mail any of your colleagues? If so, please include their Methods to Control for e-mail addresses here: Confounding ______Please fax to: (919) 919-843-5563 or mail to: North Carolina Center for Public Health Preparedness We are on the web! The University of North Carolina at Chapel Hill http://www.sph.unc.edu/nccphp Campus Box 8165 Chapel Hill, NC 27599-8165 Or go online: http://www.sph.unc.edu/nccphp/focus/

North Carolina Center for Public Health Preparedness—The North Carolina Institute for Public Health