Case Study: Mercury Exposure Monitoring at a Residential Homes Development Site

Sysco Environmental Ltd conducted a detailed inspection and chemical sampling of the underground ductwork at Former Hospital Development site. The inspection aimed to identify chemical contamination in the underground ductwork, determine contamination sources, and assess health risks to employees and residents. Concerns about air quality arose due to reported frequent headaches among workers and residents, potentially linked to contamination within the underground ductwork system. The objective of our contamination survey was to evaluate the site for the presence of a variety of airborne contaminants and establish whether there is a potential risk to workers on site and residents living in the nearby areas.

Our Contamination Survey Methodology

Sysco Environmental Ltd's lead surveyor conducted the inspection using a comprehensive approach involving personal samplers, portable meters, and chemical analysis to monitor airborne particulates and vapours. The methodology included a series of preliminary site meetings with key stakeholders to discuss the potential contamination issues and specific concerns raised by workers and residents. A desktop study was carried out to identify likely sources and target contaminants based on historical usage of the site and previous environmental reports.
 
Following the preliminary assessment, the most appropriate monitoring, sampling, and analytical methods were selected. This included personal samplers for real-time exposure measurement, portable meters for on-site gas concentration monitoring, and chemical analysis to ensure precise identification of contaminants. The sampling strategy focused on volatile organic chemicals, aldehydes, hydrogen cyanide, mercury vapours, carbon monoxide, hydrogen sulphide, ammonia, and low levels of radiation sources.
 
To ensure accuracy and compliance, relevant evaluation guidelines from the UK Health and Safety Executive (HSE) and the American Conference of Governmental Industrial Hygienists (ACGIH) were identified and applied. This comprehensive approach was designed to provide a detailed assessment of air quality and identify any potential health risks associated with chemical exposure in the underground ductwork.

Chemical Contamination Survey Results Evaluation

 
The evaluation involved comparing personal exposure levels with Workplace Exposure Limits (WELs) from UK HSE and ACGIH guidelines. Key contaminants and their limits included: The results indicated normal environmental levels for carbon dioxide, carbon monoxide, sulphur dioxide, hydrogen sulphide, ammonia, and chlorine gas. These gases are often present in small quantities in various environments, but their levels in this case were within safe limits, suggesting no immediate risk from these contaminants.
 
Carbon Dioxide (CO2): In confined spaces like old underground ducts, elevated CO2 levels can accumulate due to lack of ventilation. Biological sources of COâ‚‚2 include the natural decay of organic matter and microbial respiration. Over time, these processes can lead to significant accumulation of CO2, posing a risk of oxygen displacement and suffocation.
 
Carbon Monoxide (CO): In an old, poorly ventilated underground duct, carbon monoxide can be especially dangerous. Historical use of combustion engines or heating systems can leave residual CO. Additionally, CO can be produced by anaerobic bacterial activity, particularly in oxygen-depleted environments. This colourless, odourless gas can cause severe health risks, including headaches, dizziness, and potentially fatal poisoning without proper ventilation.
 
Sulphur Dioxide (SO2): Residual SO2 in confined spaces can originate from past industrial activities involving fossil fuels or metal extraction. Biological sources of SO2 include the decomposition of sulphur-containing organic matter by bacteria. In such environments, accumulated SO2 can pose respiratory hazards, irritating the respiratory system and exacerbating conditions like asthma.
 
Hydrogen Sulphide (H2S): Known for its rotten egg smell, H2S can accumulate in confined, poorly ventilated spaces like old underground ducts. Biological sources of H2S include the anaerobic decomposition of organic matter by sulphate-reducing bacteria. This gas can pose significant respiratory hazards and, at high concentrations, can be fatal.
 
Ammonia (NH3): In confined spaces of old industrial sites, ammonia can linger from past uses in refrigeration or chemical production. In a hospital setting, ammonia is often used as a cleaning agent and in the sterilisation of equipment. Its presence in underground ducts can cause irritation to the eyes, skin, and respiratory system, making it particularly dangerous in such confined spaces.
 
Mercury vapour levels, however, were significant but varied across different areas. In the external areas, mercury vapour was undetectable, measured at 0 mg/m3, indicating no contamination in the ambient air outside the ducts. However, in the underground ducts, mercury vapour levels reached up to 0.1 mg/m3, which exceeded occupational limits in specific areas. Mercury, a potent neurotoxin, is particularly concerning in such environments due to its ability to persist and accumulate, leading to serious health effects upon prolonged exposure. Its presence in the underground ducts of the former hospital is likely due to historical medical equipment and practices that used mercury, as well as the age and condition of the infrastructure, which can contribute to residual contamination. This significant variance in mercury vapour levels underscores the need for targeted decontamination efforts to mitigate potential health risks. In old, confined underground ducts, mercury vapour is a significant concern due to its persistence and potential to accumulate over time. In hospitals, mercury was historically used in thermometers, blood pressure devices, and other medical equipment. Residual mercury from these sources can leave behind vapours that are potent neurotoxins. Even low levels of mercury vapour can cause serious health issues with prolonged exposure, necessitating stringent decontamination efforts.

Radiological Contamination Survey

 
In an old hospital environment, particularly one with practices dating back more than 30-40 years, certain medical and diagnostic procedures could have produced low-level radiation contaminants that might eventually make their way into the waste system. One of the potential sources are radiopharmaceuticals used in diagnostic imaging and treatment, which can contain isotopes like technetium-99m, iodine-131, and others. Improper disposal of these substances, or their residual presence in patients' bodily fluids, could lead to contamination of the hospital's waste system. Furthermore, X-ray film processing involved chemicals that might become contaminated with trace amounts of radioactive material used in radiographic procedures. Equipment used for radiation therapy, including older cobalt-60 or cesium-137 sources, could contribute to low-level radioactive contamination if not properly managed. Spills, leaks, or improper disposal of equipment and materials used in these treatments could lead to residual contamination. It is important to consider older laboratory equipment, such as scintillation counters and certain types of gamma counters, which used small amounts of radioactive materials. If these were improperly disposed of or leaked, they could contribute to low-level radiation contamination. Practices from decades ago might not have included stringent protocols for the disposal of nuclear medicine waste. This could result in radioactive isotopes entering the waste system through sinks, drains, or improper disposal methods.
 
Given the age of these practices, it is plausible that residual low-level radiation contaminants could have accumulated in the waste system of an old hospital, especially in confined spaces such as underground ducts. These contaminants, while typically low in concentration, could pose long-term health risks if not identified and managed properly.

Contamination Survey Project Conclusions

 
The results of the monitoring showed that carbon dioxide levels within the underground ductwork were within normal environmental ranges, indicating that the ventilation in these confined spaces was adequate to prevent the build-up of this gas. This finding is crucial as it suggests that there is sufficient air exchange to mitigate the risks associated with elevated carbon dioxide concentrations, which can displace oxygen and pose asphyxiation hazards.
 
Regarding other major gases, the analysis did not detect sulphur dioxide, hydrogen sulphide, ammonia, or carbon monoxide in any of the sampled areas. The absence of these gases, which are common industrial contaminants, indicates that there are no immediate risks of acute exposure to these toxic substances in the confined spaces of the underground ducts. This is a positive outcome, as it suggests that historical industrial activities have not left a harmful legacy of these particular contaminants in the environment.
 
The evaluation of radiation levels showed that they were consistent with normal environmental background levels. This finding implies that there are no significant sources of ionising radiation within the ductwork, which could have originated from past medical or industrial equipment. This reduces concerns about potential radiation exposure risks to workers and residents.
 
Aldehydes and volatile organic compounds (VOCs) were detected during the assessment, but their concentrations were found to be well below the established occupational exposure limits. This indicates that while these substances are present, likely from historical use of various chemicals and solvents, they do not currently pose a significant health risk. Continued monitoring is advisable to ensure that their levels remain low and do not increase due to ongoing or future activities.
 
Mercury vapour levels were a significant concern, with substantial concentrations detected in the underground ducts. The presence of mercury, particularly in older hospital settings where it was commonly used in medical devices and equipment, necessitates immediate decontamination efforts. The elevated levels of mercury vapour pose a serious health risk due to its neurotoxic properties, and appropriate measures must be taken to clean the contaminated areas to ensure the safety of all personnel accessing these spaces. The detection of mercury highlights the importance of rigorous environmental assessments and the implementation of comprehensive decontamination procedures to address legacy contaminants in older industrial and medical facilities.
 

Recommendations

 
Based on the findings of the project, several critical recommendations are proposed to address the detected contamination and ensure a safe environment for workers and residents.
 
Immediate intervention by a specialist contractor is essential to remove the mercury residues and thoroughly decontaminate the affected areas. This step is crucial to eliminate the immediate health risks posed by the elevated mercury vapour levels detected in the underground ducts. Proper decontamination procedures will involve removing contaminated materials and cleaning surfaces to prevent further exposure.
 
Access to the contaminated ducts must be restricted until the decontamination process is complete. This measure will prevent unauthorised personnel from entering potentially hazardous areas and ensure that only trained and equipped professionals handle the decontamination efforts. Sealing the ducts effectively isolates the contamination, reducing the risk of exposure.