Note: This is NDCA’s recommended protocol of response for government agencies responding to a disease cluster concern.  There is a companion protocol, “Community Action Fact Sheet” which is currently under development.

 

Concerns usually arise in communities when an apparent disease cluster or anomaly appears.  For this document, a cluster is defined as a number of health events in space and/or time that are: (1) suspected of being connected to each other, and (2) suspected of being caused by exposures to an environmental, occupational, or socioeconomic factor.

 

When concerns arise in a community regarding a potential disease cluster, we have the following recommendations for government agencies:

 

1.  Communication.  Communicate with the community first: elected officials, health officials, community activists, service clubs, and those affected by the disease anomaly. Create a communication plan that includes those most affected by the suspected cluster.   Create a community partnership to investigate the suspected anomaly. A goal for agencies is that they should establish lines of communication with community leaders and health officials within 5 business days of being notified of the concern. Most states have protocols that guide their investigations of cluster reports, and most of these protocols follow CDC guidelines.  The health department staff in the initial contact with a concerned citizen should collect information on the number and type(s) of cases, the geographic area, and time period of concern. Most important is the need to collect information from the concerned citizen about the suspected exposures and the suspected cause of the disease(s). The health department staff can then pull information on the community from a community profile database (see #9) to add to the information provided by the concerned citizen.  With all this information in hand, the staff may be able to resolve the issue by providing the citizen with information on: (1) disease incidence and prevalence, (2) latency issues, (3) how a variety of diagnoses argues against a common cause, and/or (4) by providing the citizen with information on the suspected cause (and other potential risk factors in the area of concern).

 

If the issue cannot be resolved easily, then the health department should adopt procedures that would fall under the category of “preliminary evaluation”.  At this stage, it would be important to set up a community assistance panel if possible (i.e., if the community is sufficiently organized) and to work together with the community in developing the evaluation plan. (The community must participate at the “ground floor” of decision-making).

 

2. Assess existing information.   Confirm the diagnoses of the health events.

Questions to consider:

(1) Is there a spatial and/or temporal cluster? (2) What ages did the cancers occur in? (i.e. usually of more interest in children (shorter lag time between exposure and cancer); cancer is common among older adults; (3) Are exposures occupational or population-based? (occupational would be higher exposures in general); (4) Are cancers mixed different types or one type of cancer (if the later, usually is more likely that the cancer is related to one exposure); (5) Is the cancer rare or more common type (e.g. childhood leukemia cluster vs. adult lung cancer). Staff should conduct a literature review of the diseases of interest and the suspected exposures/causes of interest.  It would also be important to determine the relevant time period for diseases to have occurred given the time period when exposures occurred (taking into account any latency issues, or windows of vulnerability such as the first trimester of pregnancy for major birth defects).

 

3. What is the geographic area of concern? The geographic area should be arrived by consensus with the concerned citizens.  It is important that the health department staff work closely with the concerned community to determine the extent of the exposed area, the levels of exposure, and the time period of exposures.  The definition of the geographic area and time period of concern should match the exposed area and the relevant time period when the exposure could have caused the health effects of concern.  The ratio of the observed number of cases vs. the expected number of cases in a specified area (e.g. census tract) is often computed at this point; (this is performed by the local cancer registry in the case of cancer). The community can help make sure the data are current; there may be recent cases which haven’t gotten entered into registries, or cases which were diagnosed out of state.  Agencies should have a goal to involve all government agencies that have jurisdiction or related interest within 30 days.

 

There is also the issue of what health events to include or not include in the investigation.  There is often a bias-precision tradeoff.  Including more cases increases your precision (and statistical power) but may introduce bias (e.g., by including diseases that are not relevant to the exposure).  On the other hand, restricting the number of cases may minimize bias but decrease your precision.  The decision to include or exclude health events should be done by consensus with the community.  It should also be based on a causal hypothesis: given the levels and type of exposure and the time period of exposure, what health effects would be expected?  What health events are similar in terms of etiology or pathogenesis?

 

4.  Look for environmental exposures. First, review if ambient exposures are exceeding accepted standards.  If so, the first step should be to ameliorate current exposures. Perform a general environmental exposure assessment with community support and involvement.  If a clear route of exposure is established, biomonitoring can be considered as an important component of this assessment,, if laboratory methods exist for the compound of concern (note: many agents cannot or should not be biomonitored because no lab test exists, the agent may be rapidly excreted or metabolized from body (i.e. short half-life), or the exposure occurs in the past and no current exposures exist).   Samples should be archived. In most cases, biomonitoring will not be useful because the relevant exposures likely occurred in the past and, except for chemicals that are persistent in the body, would not be detected.[1] If the exposure is ongoing, then the assumption can be made that current levels mimic past levels, then biomonitoring may be effective.  However, one must take into account other sources of exposure because biomonitoring integrates all the sources (e.g., a test for benzene would pick up exposure from a toxic waste site and also exposure while pumping gas; a test for PCE would pick up exposure from the contaminated drinking water and exposure from one’s clothes just back from the dry cleaners, etc.).

A list of the possible exposures of interest should be generated. Any data that exists on environmental contaminants preceding the cluster event should also be made available to the community (water, TRI, air, hazardous waste releases, radiation releases, EIRs, and permitting, etc.)

 

Any environmental data that does exist should be sought after.  It may be necessary to reconstruct historical exposures using modeling techniques.  Involvement of researchers with expertise on exposure assessment modeling may be necessary.

5. Environmental Testing Results. Results from any testing should be made available to the public within 10 days.  The public should be encouraged to analyze the data itself; the public should have access to all environmental testing data including chain of custody, and raw lab results.   The community has the right to test along side of agency with their own independent labs, they should be part of the process if desired to do split sampling.  Contaminants not tested for should be included in the reporting.

6. Community Access.  The community will have access to all health registry data, either smoothed or aggregated to comply with confidentiality laws.  This data should be made available to the community within 30 days.

7. Health Survey. Assess whether a health survey is beneficial or needed at this point.   If a health survey is performed, the community should be an integral part of the effort.  A partnership should be formed with the community to perform the survey. The decision to conduct a study or exposure investigation or health survey should be achieved by consensus with the community.  However, it is important that a community understand what a study/survey/investigation entails, what it can and cannot accomplish, and the risky nature of the effort.  The health department staff can facilitate this discussion.

8.  Next Steps.  At the end of the investigation if there is no obvious environmental link to the disease cluster or there are toxic exposures in the community yet no consensus about the link to illness, then what are the next steps?  As with all the steps in an investigation/study, the community must participate in the decision-making at the ground floor.  Very few cluster investigations have successfully identified a cause.  This is a point that the health department should relate to the community very early on during the deliberations about whether to conduct an investigation in the first place.     The study or investigation should have already been using the best scientific methods.  If it fails to identify a cause, then the next step for the community is to identify other strategies that might accomplish their goals/needs.

 

9. Community Environmental Hazard Database.  Health agencies should develop a “community profiles” database, so that staff can quickly access data for each town on a wide variety of environmental/occupational/SES factors and health data such as: public drinking water contamination, air toxics levels, fish advisories, NPL information (e.g., site location, exposure pathways, contaminants in the pathways that are of concern), TRI sites (location, air emissions, information on chemicals used in the workplace), landfills/waste dumps/waste transfer locations, traffic density hot spots, agricultural pesticide use, groundwater contamination plumes, radon hazard areas, relevant census data, and health data (e.g., how the community compares to the state rates for cancers, birth defects, low birth weight, preterm birth, and small for gestational age). With such a database, the health dept can react quickly to community concerns as well as act pro-actively to identify communities at risk.

 

Written April 2009, NDCA Science & Policy Committee