Mercury is one of the most common and hazardous contaminants in health care and biomedical research facilities, particularly in older facilities where mercury was widely used and often spilled. Even small amounts of mercury can be spread rapidly, contaminating large areas and systems above safe levels, and contamination can persist for long periods of time without detection. Often spilled mercury is only revealed during renovation and demolition activities that expose areas under equipment, floor tiles and in plumbing systems.
Assessment and Remediation
Protocols used for assessment and remediation of hazardous substances in facilities undergoing renovation, demolition or other deconstruction processes are referred to as decommissioning.
No single method or system for assessment of mercury contamination is appropriate for all situations. Methods selected for assessment of mercury in facilities must consider several factors, including but not limited to the:
- Past history of use in the area
- Expected chemical form(s) of mercury
- Media to be assessed – air, liquids, surfaces, solids etc.
- Total versus extractable mercury
- Regulatory requirements
- Interferences posed by other chemicals in the areas or items surveyed
- Capability to detect mercury at levels of concern - required sensitivity and detection limits
- Speed required for screening of areas and materials
- Intended next use of materials – reuse, recycling or disposal
- Waste recycling and disposal criteria
- Ability to maintain adequate temperatures in the areas being assessed
- Cost and availability of assessment instrumentation
- Presence as intrinsic versus contaminant levels
Data from previous assessments of similar facilities can be very helpful in developing and streamlining assessment and remediation methods.
Decommissioning Pilot Project
Assessment Checklist (to come)
Flowchart (to come)
The procedures used by NIH were initially tested a pilot project carried out before selective demolition of a laboratory building on the Bethesda Campus. Data from this and subsequent projects have been used to develop tools and update standard for use in future projects. These tools include an assessment checklist for hazardous substances (intrinsic materials and contaminants) and a flowchart showing the screening methods and disposition of common waste materials generated during deconstruction of biomedical facilities. Because mercury is such a common contaminant and it is subject to regulation at very low levels it is a primary determinant for the disposition of debris materials from biomedical facility deconstruction processes.
Mercury in Plumbing Systems
Mercury is a very common contaminant in wastewater plumbing and laboratory vacuum systems. In older biomedical facilities and laboratories much of this contamination is a legacy of past uses of mercury, primarily in thermometers and disposal of mercury containing spills and wastes via drains. Since elemental mercury (liquid metal) is very heavy – about 13.5 times denser than water it rapidly settles in to the bottoms of traps, joints and other low areas of systems where it can reside for very long periods of time.
Even in newer facilities that have eliminated most uses of mercury and prohibit all on-site disposal significant amounts of mercury can be found in wastewater systems. This is because many common chemicals such as bleach that are ultimately discharged into wastewater systems after use contain mercury as a contaminant. While the concentration of dissolved mercury in the discharged wastewater may be very low the mercury can be accumulated in solid biofilms (biomass) and sediments to levels that are many times higher than in the water. Increased flow rates, turbulence or other conditions can cause these solids to be released from plumbing resulting in elevated concentrations the wastewater. Since the maximum concentration of mercury allowed in wastewater discharges is extremely low in many jurisdictions the release of these contaminated solids my result in violations of pollution control regulations.
An extensive amount of information on the sources of mercury accumulation in plumbing and reduction strategies has been developed. This is largely the product of investigations conducted by a working group comprised of the Massachusetts Water Resource Authority (MWSA) and the Medical Academic and Scientific Community Organization (MASCO), a not-for-profit provider of services and technical assistance to medical and academic institutions in the Longwood, MA area. MASCO Research Reports, Pretreatment Manual, Mercury Management Guidebook and a database of Mercury content in products
Microbial Interactions with Mercury
Microbial interactions may increase the environmental toxicity of mercury contaminants released with wastewater and result in other subsidiary hazards.
Mercury compounds have long been used as fungicides, disinfectants, preservatives and until recently, as drugs for treatment of infectious diseases. While these compounds are toxic to most microorganisms, some bacteria have developed mechanisms to survive and grow in the presence of lower concentrations of mercury. These mechanisms have probably existed since primordial times as an adaptation to life in environments where mercury is naturally present. Adaptations to mercury toxicity also allow bacteria to survive and grow in mercury contaminated plumbing and other artificial environments. In these situations the adaptive mechanisms that allow bacteria to persist may have undesirable consequences including development of resistance to antibiotics in other resident bacteria, and accumulation and subsequent biotransformation inorganic forms of mercury into organic compounds such as dimethylmercury, which are more toxic to animals and highly persistent and bioaccumulative in the environment. Even at very low levels of exposure mercury is also a potent suppressor of the immune response of mammals to some infectious agents.
Mercury is common contaminant in health care and biomedical research facilities, especially in older facilities that were in operation before restrictions on mercury use and disposal were established. The potential contribution of mercury to the development of antibiotic resistance in pathogenic bacteria and interference with immune responses is of particular concern in facilities where patients and laboratory animals, some with compromised immune responses are likely to be present. Mercury may also interfere with sensitive research protocols carried out in contaminated facilities.
Further information on mercury contamination in plumbing and microbial interactions is available in these presentations: