A study of the potential release of bioaerosols from containers as a result of reduced frequency residual waste collections

Abstract

Microorganisms have the potential to grow within waste containers if waste is stored for longer periods as a result of an extended residual waste collection cycle. Release of microorganisms as bioaerosols during waste collection and processing may be an occupational risk to workers within the industry. There may be many constituents of the bioaerosol that may be of concern, however, there are currently only workplace exposure limits proposed for endotoxin (90EUm−3). A field-scale trial was established to determine the concentration of mesophilic bacteria, Gram-negative bacteria, Listeria monocytogenes, thermotolerant fungi, Aspergillus fumigatus, and endotoxin and (1→3)-β-d-glucan in air within bins containing either bagged or loose residual waste, in warm (23°C) or cold (7°C) conditions, to simulate an extended collection cycle. Fresh waste was added during the first four weeks, with an additional ‘missed collection’ phase of a further four weeks where no more waste was added. A second trial examined the microbiological components of bioaerosols associated with ‘tipping’ the bins, simulating the moment when bins are emptied into waste collection vehicles. The majority of mesophilic bacteria, fungi and A. fumigatus concentrations were recorded when fresh material was added to the bins, with only mesophilic bacteria recorded up to week 6 during the ‘missed collection’ phase. (1→3)-β-D-glucan concentrations were variable throughout the first trial, (geometric mean range 0.4–13.8ngm−3). Perhaps the bioaerosol component of most interest was endotoxin (geometric mean range 0.52–1288EUm−3). Elevated endotoxin concentrations were recorded during the ‘missed collection’ phase of the extended collection cycle and during ‘tipping’. This data demonstrates significant concentrations of bioaerosols and particularly endotoxin can be generated during prolonged residual waste storage and collection. As endotoxin is a bioaerosol component of concern it can be concluded there is the potential for workplace exposure hence identifying key areas for risk assessment.