Toni Gladding

Health risks of materials recycling facilities

Eleven MRFs were investigated as part of a European Commission BIOMED2 and Environment Agency joint-funded programme. These represented different recycling facilities currently operating in the UK. Three MRFs accepted household waste via kerbside boxes, two via a green bag, two from twin-wheeled bins and two accept waste from a combination of systems. The processing capacity for these MRFs varied from 1,000 to 100,000 tonnes per annum (t.p.a.), with ‘residue rates’ of between 8% (bags and boxes), to 60% (twin-bins and mixed) of the total throughput. This study was intended to investigate a range of occupational exposures to MRF workers, work-related symptoms and effects in MRF workers and potential environmental impacts. As a result of a literature review identifying gaps in the knowledge in relation to MRF exposures (Nersting et al 1991, IEERR 1995, Sigsgaard et al 1996, Kivranta et al 1999), a variety of occupational and environmental measurements were made. Volatile Organic Compounds, Electromagnetic Fields, total and viable microorganisms, cadmium and mercury were not measured in significant amounts. However, concentrations of organic sulphur compounds below threshold levels could still contribute to gastrointestinal problems. Lead was detected in the air of one facility (2.5μg/m3), and was found in settled dust in all of the MRFs measured, but was not considered significant. Environmentally, noise and particulates were not detected in significant amounts, but retain a nuisance potential. Occupationally, noise was found to exceed recommended levels when operating some equipment and stereos, and required action from operators to protect operative’s hearing. Also occupationally, dust, endotoxin and glucan were found in excess of recommended exposure levels (10 mg/m3 for dust, 10 ng/m3 for endotoxin and glucan). Self-reported symptom questionnaires on 159 operatives also identified that when MRFs were grouped into higher vs. lower exposure groupings adjusted odds ratios showed a significant increase in symptoms experienced by operatives with higher exposures. Relevant symptoms and exposures include dust and irritated nose (2.55 (1.20-5.70)); endotoxin with cough with phlegm (2.34 (1.11-4.93)) and hoarse/parched throat (2.62 (1.21-5.67)); and glucan with chest tightness (5.31 (1.37-20.56)), cough with phlegm (2.87 (1.26-6.56)) and stomach problems (4.53 (1.22-16.85)). To a lesser extent, operatives also complained of systemic problems such as headache and influenza-type symptoms, nausea and tiredness. In the study, there was a significantly increased risk for self-reported respiratory symptoms related to higher work site exposures to endotoxin and (13)-s-D-glucan. Gastrointestinal symptoms were related to (13)-s-D-glucan exposure, gastrointestinal symptoms have previously been associated to (13)-s-D-glucans and endotoxin exposure (Thorn et al 1998, Ivens et al 1999). In addition in two MRFs monitored from start-up blood data from eight operatives new to the industry shows a significant decrease in lymphocytes (p=0.013), monocytes (p=0.001) and neutrophils (p=0.001) over a period of 10 months. This potentially reflects an inflammation in the lungs, where cells decrease in the blood because they are recruited to the lung as part of an inflammatory response. The conclusions of this research are that biological agents present in the air at MRFs have the potential to be harmful to the health of operatives working in these plants. These occupational exposures are derived from close contact with waste materials, which exposes the worker to a localised aerosol of organic dusts from organic residues and contaminants (food and drink residues) within materials received. The effect of temperature and time on decomposition of these organic contaminants in the period after it is discarded and before collection may affect the amount of bioaerosols generated although no seasonal variations were detected in this study (unlike Thorn 2001). However, methods of handling materials were shown to affect exposure. Using chi-square tests comparing exposures in the MRFs, those that were twin-bin fed showed significantly higher exposures to dust and endotoxin, and also showed the highest amount of residue in the materials received. This study recommends an interim approach to dealing with these potential issues until more data becomes available; exposures can be mitigated through a variety of measures. An overview of the possible solutions include targeting the quality of incoming materials, examining MRF design and materials handling, and ensuring regular housekeeping and maintenance procedures in conjunction with information, education and training on personal hygiene for MRF workers.

Scoping studies to establish the capability and utility of a real-time bioaerosol sensor to characterise emissions from environmental sources

A novel dual excitation wavelength based bioaerosol sensor with multiple fluorescence bands called Spectral Intensity Bioaerosol Sensor (SIBS) has been assessed across five contrasting outdoor environments. The mean concentrations of total and fluorescent particles across the sites were highly variable being the highest at the agricultural farm (2.6 cm-3 and 0.48 cm-3, respectively) and the composting site (2.32 cm-3 and 0.46 cm-3, respectively) and the lowest at the dairy farm (1.03 cm-3 and 0.24 cm-3, respectively) and the sewage treatment works (1.03 cm-3 and 0.25 cm-3, respectively). In contrast, the number-weighted fluorescent fraction was lowest at the agricultural site (0.18) in comparison to the other sites indicating high variability in nature and magnitude of emissions from environmental sources. The fluorescence emissions data demonstrated that the spectra at different sites were multimodal with intensity differences largely at wavelengths located in secondary emission peaks for λex 280 and λex 370. This finding suggests differences in the molecular composition of emissions at these sites which can help to identify distinct fluorescence signature of different environmental sources. Overall this study demonstrated that SIBS provides additional spectral information compared to existing instruments and capability to resolve spectrally integrated signals from relevant biological fluorophores could improve selectivity and thus enhance discrimination and classification strategies for real-time characterisation of bioaerosols from environmental sources. However, detailed lab-based measurements in conjunction with real-world studies and improved numerical methods are required to optimise and validate these highly resolved spectral signatures with respect to the diverse atmospherically relevant biological fluorophores.

The challenges, uncertainties and opportunities of bioaerosol dispersion modelling from open composting facilities

Bioaerosols are ubiquitous organic particles that comprise viruses, bacteria and coarser fractions of organic matter. Known to adversely affect human health, the impact of bioaerosols on a population often manifests as outbreaks of illnesses such as Legionnaires Disease and Q fever, although the concentrations and environmental conditions in which these impacts occur are not well understood. Bioaerosol concentrations vary from source to source, but specific human activities such as water treatment, intensive agriculture and composting facilitate the generation of bioaerosol concentrations many times higher than natural background levels. Bioaerosols are not considered ‘traditional’ pollutants in the same way as PM10, PM2.5, and gases such as NO2, and consequently dispersion models do not include a bespoke method for their assessment. As identified in previous studies, priority areas for improving the robustness of these dispersion models include: 1) the development of bespoke monitoring studies designed to generate accurate modelling input data; 2) the publication of a robust emissions inventory; 3) a code of practice to provide guidelines for consistent bioaerosol modelling practices; and 4) a greater understanding of background bioaerosol emissions. The aim of this research project, funded by the Natural Environmental Research Council (NERC), is to address these key areas through a better understanding of the generation, concentration and potential dispersion of bioaerosols from intensive agricultural and biowaste facilities, using case studies developed at specific locations within the UK. The objective is to further refine existing bioaerosol monitoring and modelling guidelines to provide a more robust framework for regulating authorities and site operators. This contribution outlines the gaps that hinder robust dispersion modelling, and describes the on-site bioaerosol data collection methods used in the study, explaining how they might be used to close these gaps. Examples of bioaerosol dispersion modelled using ADMS 5 are presented and discussed.