COVID-19: Are we safe from our own trash?
COVID-19 has had many impacts on the generation and management of solid waste. The shift to mostly working at home translates to increased generation of waste in the residential sector, while commercial waste that is generated at offices, stores, restaurants, stadiums and the like, has decreased. Changes in waste generation patterns have resulted in shifts in waste collection schedules and how vehicles are utilized, presenting challenges to route planners and schedulers.
In addition, there has been a huge increase in the generation of waste masks, gloves and other personnel protective equipment, although this is likely a small fraction of the waste stream. Finally, increased e-commerce has resulted in more cardboard boxes in residential waste.
Perhaps most important is worker safety. Is the garbage belonging to people infected with SARS-CoV-2 a potential source of community spread and a threat to sanitation workers? Let’s consider this from a few perspectives, but first let’s recognize that workers involved in refuse collection and disposal are essential. If you wonder why, then consider what happens when solid waste is not collected.
Before considering COVID-19, recognize that garbage contains many noxious and potentially infectious items, so separating sanitation workers from the materials that they handle has always been important. Issues surrounding COVID-19 are certainly more worrisome because of the high incidence of the virus in some areas, the potential for asymptomatic spread among workers and the absence of a cure at this time.
The major points of contact between sanitation workers and garbage occur during collection, at sorting plants in the case of recyclable materials (known as MRFs or Materials Recovery Facilities), at transfer stations and at combustion facilities and landfills. In the case of collection, the best protection is the use of automated or semi-automated collection vehicles. In this scenario, residents are issued a cart that can be lifted by a robot arm and emptied into a truck with no human contact. While some aerosols and particles may be generated when the cart is emptied, the cart is distant from the sanitation worker and it is outdoors, where rapid air dilution occurs. Similarly, commercial waste is typically collected from dumpsters using automated equipment that does not require close contact between the waste and the worker. In the residential sector, there is some manual collection in some cities and rural areas. Here, there could be risks associated with open bags and loose garbage that is theoretically infectious, whether with COVID-19 or other medical waste generated in the home, such as needles or contaminated bandages. Workers are readily protected by wearing masks and gloves and practicing good sanitation.
The virus, SARS-CoV-2, decays naturally on surfaces such as cardboard and plastic. The half-life (time to decay to half the original concentration) on cardboard is two to four hours, and six to eight hours on plastic under laboratory conditions. This implies that most of the virus would be non-infectious on typical waste surfaces after several days, and only the most recently discarded garbage from infected residents would present even a potential risk to sanitation workers. While the spread of COVID-19 due to fomites (particles on surfaces) is theoretically possible, the role of environmental contamination, particularly through resuspension of settled particles on surfaces is widely debated. The current emerging consensus is that transmission through fomites is possible, but a minor pathway compared to person-to-person transmission, and to date there are no specific reports which have directly demonstrated fomite transmission.
A second point of exposure is at MRFs that typically sort mixed recyclables (various boxes and paper, plastic and glass containers, and metal) and sometimes sort mixed residential waste. While many facilities are automated, there are nonetheless workers at various points on picking lines to remove non-recyclable material (e.g., plastic films, non-recyclable plastics). In theory, surface contamination through disposal could have occurred one to 14 days prior to the material arriving at a MRF. Thus, while the probability of infectivity is low, it behooves workers to wear gloves and masks. Masks may be as useful for dust as for airborne pathogens. Gloves also greatly reduce the touching of the mouth, eyes and nose. Together, with periodic and proper handwashing, transmission through surfaces is greatly reduced. Finally, workstations can be arranged to keep workers apart and barriers can be installed between workers depending on air flow patterns.
Once collected, waste is transported to a transfer station where it is transferred to larger vehicles for long distance transport, or taken directly to a landfill or combustion facility. When waste is emptied onto a floor at a transfer station — outside at a landfill or into a pit prior to combustion — bags will break and particles and aerosols may be released. The science on aerosol generation from municipal solid waste (MSW) transfer stations is limited, but the few studies show an increase in aerosols in indoor transfer stations. In all cases, masks largely mitigate the potential transmission of SARS-CoV-2, as well as other contaminants such as particulate matter and microorganisms. The outside environment of a landfill and air flow patterns at combustion facilities offer further protection.
To conclude, sanitation workers can do their jobs and be readily protected using many of the same protocols advised of the general public — wear gloves and a mask, and maintain distance from co-workers. While every work environment is different, behavior outside of work may be more important in stopping the spread of COVID-19. This discussion is applicable to regions of the world where solid waste management infrastructure is reasonably well-developed and contrasts with underdeveloped regions where people work and live next to landfills to manually recover recyclables for sale.
Dr. Morton A. Barlaz is a professor and head of the Department of Civil, Construction, and Environmental Engineering at North Carolina State University.
Francis L. de los Reyes III is a professor of Civil, Construction, and Environmental Engineering, associate faculty of Microbiology, and training faculty of Biotechnology at North Carolina State University.
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