Understanding Environmental Sampling for the Novel Coronavirus (SARS-CoV-2): FACS Update #8


The world of the novel Coronavirus continues to change rapidly.  As shelter in place orders are lifted and the important decision to re-occupy is made, the need to provide assurance that indoor environment is safe to re-occupy becomes more necessary.  And demand for environmental testing is on the rise. Not only is the demand for environmental testing growing, but the number of companies, laboratories and other organizations offering testing has increased.  Email inboxes are being flooded and advertisements providing information about COVID-19 or offers to clean, disinfect and test seem ubiquitous these days.  But sampling can be complicated, costly and the results difficult to interpret. What does all this mean?

Providing assurance to employees and the general public that your facility is adequately safe may appear to be an easy goal to meet. Simply answer one of the many ads, hire a company to test your environment, and get an all clear. However, hidden in this process are a number of potential pitfalls. Did the company you hired to test perform the appropriate sampling? Were an adequate number of samples collected? Were proper sampling methods and techniques employed? Did they sample for the presence (or absence) of the novel Coronavirus or to evaluate the effectiveness of cleaning measures?  Did they just collect samples and a lab report, or did they perform a more complete risk assessment, provide interpretation of the results, evaluate safe work practices, and verify the efficacy of cleaning and disinfection?

Partnering or engaging with a knowledgeable environmental health professional is an important factor to consider when deciding how and when to perform environmental testing. If testing is determined to be a necessary part of reoccupancy plans, or to meet other objectives, a knowledgeable professional can guide you on the methods most applicable to your specific circumstances and develop an effective sampling plan.  The decision to test should consider overall risks, in-house safe work practices, cleaning and disinfection protocols proposed and in consideration of the most up-to-date guidance from reputable organizations such as the Centers for Disease Control and Prevention (CDC), World Health Organization (WHO), and the Occupational Safety and Health Administration (OSHA).

With respect to the novel Coronavirus (SARS-CoV-2), one primary objective of environmental sampling may be to reliably represent that an environment has been effectively cleaned and disinfected and risk to the occupants has been reduced. Unfortunately, while collecting environmental samples can help to validate that surfaces have been decontaminated according to an established policy, they cannot guarantee that surfaces or indoor air are free of contamination. Nor can testing alone be relied on to assess risk to occupants. Fortunately, a knowledgeable environmental health professional can provide informed guidance.

Environmental sampling can be performed by targeting a specific agent or pathogen of concern, in this case SARS-CoV-2, or performing surrogate sampling, which is sampling for the detection of a similar or non-specific agent to represent cleanliness, proper disinfection, or to assess a level of risk.  While surrogate sampling may be less costly, more easily deployed, and under the right circumstances, a reasonable alternative to verify the efficacy of cleaning and disinfection, it fundamentally cannot answer the question of whether the novel Coronavirus is or more importantly, is not present.

Currently, the most reliable means of analysis for SARS-CoV-2 is by real-time quantitative Reverse Transcriptase Polymerase Chain Reaction (real-time qRT-PCR).  Using the unique genetic material of the virus, viral ribonucleic acid (vRNA), laboratories can reliably detect and report the amount of viral material present in an air or surface sample.

The advantage of real-time qRT-PCR method is it is agent specific and reports the presence or absence of SARS-CoV-2 viral RNA in the sample. This method is sensitive and able to detect very small amounts of viral RNA present in samples. Unfortunately, this method does have limitations; for example, it cannot differentiate between virus that is capable of infection or one that is inactive and occasionally false positives can occur. Further, no guidelines have been developed to select the location and number of samples to collect and how to interpret the results to conclude that an environment is free of risk.

While not agent specific like real-time qRT-PCR, use of testing for surrogates is not without value. Applications of potential agent-specific or surrogate agent sampling applications may include, but are not limited to:

  • assessing personal, particularly healthcare professional, exposure to aerosol or droplets contaminated with SARS-CoV-2;
  • assessing the extent and persistence of surface contamination to identify areas or objects that may be important for transmission of the virus;
  • identifying surfaces that may require more frequent cleaning and disinfection, or establish a cleaning and disinfection plan;
  • identify “before” cleaning data for interpretation of post-cleaning and disinfection data;
  • validating the efficacy of established cleaning and disinfection protocols; and
  • collecting data to support building re-occupancy or document an insurance claim associated with business interruption or other insurance coverage.

Common agents used to evaluate the efficacy of cleaning and disinfection programs or for testing the environment before and after cleaning can include:

  • Testing for bacteria that are susceptible to the same cleaning methods and disinfecting agents as SARS-CoV-2;
  • Testing for Adenosine triphosphate (ATP) which is generated by all living organisms as an indicator of general biological contamination;
  • Sampling for particulate matter using polarized light microscopy to look at the types of particles present as a general indicator of cleanliness; or
  • Mycometer surface sampling which looks for a fungi-specific enzyme, typically used for assessments related to mold contamination.

Each of these methods has some value but also very important limitations.  For example, viruses do not produce ATP, so use of ATP will not identify is SARS-CoV-2 is present in the sample analyzed.  ATP samples can be impacted by residual disinfectant resulting in false negatives. When using bacterial or mold surrogate methods, consideration of the bacteria involved, the disinfectants used and the impact of residual disinfectant on surfaces is necessary.

Regardless of the method selected, it is important to have a sampling plan prepared by a qualified environmental health professional that considers the impact of the activities in the building, the cleaning and disinfection methods used, how long it has been since the cleaning was performed, the location and number of samples to be collected, whether a combination of sample types is needed, how the data will be interpreted and what actions will be taken after results are received.  These plans should be prepared and the interpretation methodology and contingency plans discussed prior to collection of samples.

As noted earlier in this post, there are currently no regulatory or guidance thresholds for safe levels of SARS-CoV-2 in building air or on surfaces of varying types. It is also important to recognize that the lack of detection of SARS-CoV-2 in environmental samples does not determine that the surface or air assessed is free of viral contamination, only that SARS-CoV-2 virus was not detected in the sample area at the time of sampling and above the laboratory method of detection.

If you or your business are in need of environmental sampling support or assistance, FACS experts can help to provide guidance to ensure sampling techniques and strategies are applied appropriate to meet your individual objectives. Please contact us if you have any questions or if our experts can be of assistance in managing your pandemic response. You can also call FACS at (888) 711-9998.