Highlights
Coronavirus on workplace environmental surfaces is associated with presence of asymptomatic spreaders and can be used to verify effectiveness of COVID-19 control practices.
Workplace locations with several positive Coronavirus contaminated surfaces were 10 times more likely to have SARS-CoV-2 employees than locations with few or no contaminated surfaces.
Environmental surface testing results can be used to inform the need for employee testing.
A total of 115 Danish dwellings were investigated during the winter season in order to evaluate the indoor environment. The sample was considered representative of Danish dwellings. Measurements of air‐exchange rates in the bedrm showed a very low natural venthtion with a median air‐exchange rate of 0.28 air changes per hour (ach) (interqmmle range (IQR): 0.12 –0.56).18% of the dwellings had a natural air‐exchange below a detectable limit of 0.10 ach and 72% had air‐exchanges rates below the requirements in Danish Building Codes of 0.50 ach. The investigations showed a statistically signifiant inverse correlation between air‐exchange rates and absolute indoor humidity. Concentrations of formaldehyde and volatile organic compounds were measured in 36 dwellings. The median formaldehyde concentration was 0.037 mg/m3 which is well below the recommended indoor TLV The concentration of VOC in some cases reached a level that may be of importance for persons with sensitive airways. It is concluded that natural ventilation in a great number of Danish dwellings is too low fiom a health point of view and that the requirements in Danish Building codes are insufficient to ensure acceptable air‐exchange rates.
A dynamic system for the generation of stable hydrogen peroxide test atmospheres was applied to the evaluation of samplers used for the determination of hydrogen peroxide in workplace air. The system is able to generate gas mixtures of between 0.1 and 10 ppm at different combinations of relative humidity (20-80%) and temperature (10-30 degrees C). Gaseous hydrogen peroxide is sampled on glass filters impregnated with Ti(IV) chloride and sulfuric acid and analyzed by UV spectroscopy. An interference was observed due to the acid catalyzed decomposition of peroxyacetic acid to hydrogen peroxide. This was significantly reduced by applying high sample flow rates and by lowering the concentration of sulfuric acid. The performance of the sampler and sources of uncertainties were tested according to the European Standard EN 1076.
Detecting all workplace asymptomatic COVID-19 virus spreaders would require daily testing of employees, which is not practical. Over a two week period, nine workplace locations were chosen to test employees for SARS-CoV-2 infection (841 tests) and high-frequency-touch point environmental surfaces (5,500 tests) for Coronavirus using Eurofins COVID-19 SentinelTM RT-PCR methods. Of the 9 locations, 3 had one or employees infected with SARS-CoV-2, neither of whom had symptoms at the time of testing nor developed symptoms. Locations with Coronavirus contaminated surfaces were 10 times more likely to have clinically positive employees than locations with no or very few positive surfaces. Break room chairs, workbenches, and door handles were the most frequently contaminated surfaces. Coronavirus RNA was detected at very low concentrations (RT-PCR 34 to 38 Cq). Environmental monitoring can be used to validate intervention strategies and be useful to verify the effectiveness of such strategies on a regular basis.
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