Birgitte Herbert Nielsen

Collection of domestic waste. Review of occupational health problems and their possible causes.

During the last decade, a growing interest in recycling of domestic waste has emerged, and action plans to increase the recycling of domestic waste have been agreed by many governments. A common feature of these plans is the implementation of new systems and equipment for the collection of domestic waste which has been separated at source. However, only limited information exists on possible occupational health problems related to such new systems. Occupational accidents are very frequent among waste collectors. Based on current knowledge, it appears that the risk factors should be considered as an integrated entity, i.e. technical factors (poor accessibility to the waste, design of equipment) may act in concert with high working rate, visual fatigue due to poor illumination and perhaps muscle fatigue due to high work load. Musculoskeletal problems are also common among waste collectors. A good deal of knowledge has accumulated on mechanical load on the spine and energetic load on the cardio-pulmonary system in relation to the handling of waste bags, bins, domestic containers and large containers. However, epidemiologic studies with exposure classification based on field measurement are needed, both to further identify high risk work conditions and to provide a detailed basis for the establishment of occupational exposure limits for mechanical and energetic load particularly in relation to pulling, pushing and tilting of containers. In 1975, an excess risk for chronic bronchitis was reported for waste collectors in Geneva (Rufèner-Press et al., 1975) and data from the Danish Registry of Occupational Accidents and Diseases also indicate an excess risk for pulmonary problems among waste collectors compared with the total work force. Surprisingly few measurements of potentially hazardous airborne exposures have been performed, and the causality of work-related pulmonary problems among waste collectors is unknown. Recent studies have indicated that implementation of some new waste collection systems may result in an increased risk of occupational health problems. High incidence rates of gastrointestinal problems, irritation of the eye and skin, and perhaps symptoms of organic dust toxic syndrome (influenza-like symptoms, cough, muscle pains, fever, fatigue, headache) have been reported among workers collecting the biodegradable fraction of domestic waste. The few data available on exposure to bio-aerosols and volatile compounds have indicated that these waste collectors may be simultaneously exposed to multiple agents such as dust containing bacteria, endotoxin, mould spores, glucans, volatile organic compounds, and diesel exhaust. Several studies have reported similar health problems as well as high incidence rates of pulmonary disease among workers at plants recycling domestic waste.(ABSTRACT TRUNCATED AT 400 WORDS)

Sorting and recycling of domestic waste. Review of occupational health problems and their possible causes

In order to reduce the strain on the environment from the deposition of waste in landfills and combustion at incineration plants, several governments throughout the industrialized world have planned greatly increased recycling of domestic waste by the turn of the millennium. To implement the plans, new waste recycling facilities are to be built and the number of workers involved in waste sorting and recycling will increase steadily during the next decade. Several studies have reinforced the hypothesis that exposure to airborne microorganisms and the toxic products thereof are important factors causing a multitude of health problems among workers at waste sorting and recycling plants. Workers at transfer stations, landfills and incineration plants may experience an increased risk of pulmonary disorders and gastrointestinal problems. High concentrations of total airborne dust, bacteria, faecal coliform bacteria and fungal spores have been reported. The concentrations are considered to be sufficiently high to cause adverse health effects. In addition, a high incidence of lower back injuries, probably due to heavy lifting during work, has been reported among workers at landfills and incineration plants. Workers involved in manual sorting of unseparated domestic waste, as well as workers at compost plants experience more or less frequent symptoms of organic dust toxic syndrome (ODTS) (cough, chest-tightness, dyspnoea, influenza-like symptoms such as chills, fever, muscle ache, joint pain, fatigue and headache), gastrointestinal problems such as nausea and diarrhoea, irritation of the skin, eye and mucous membranes of the nose and upper airways, etc. In addition cases of severe occupational pulmonary diseases (asthma, alveolitis, bronchitis) have been reported. Manual sorting of unseparated domestic waste may be associated with exposures to large quantities of airborne bacteria and endotoxin. Several work functions in compost plants can result in very high exposure to airborne fungal spores and thermophilic actinomycetes. At plants sorting separated domestic waste, e.g. the combustible fraction of waste composed of paper, cardboard and plastics, the workers may have an increased risk of gastrointestinal symptoms and irritation of the eyes and skin. At such plants the bioaerosol exposure levels are in general low, but at some work tasks, e.g. manual sorting and work near the balers, exposure levels may occasionally be high enough to be potentially harmful. Workers handling the source-sorted paper or cardboard fraction do not appear to have an elevated risk of occupational health problems related to bioaerosol exposure, and the bioaerosol exposure is generally low.(ABSTRACT TRUNCATED AT 400 WORDS)

Exposure to Air Contaminants in Chicken Catching

A cross-sectional study of chicken catchers was carried out by personal sampling of air contaminants. The catchers used either the drawer method (DM) or truck method (TM) for loading chickens into cages. DM catchers were exposed to higher concentrations of hazardous substances than TM catchers, except for ammonia. In terms of geometric means total dust concentrations were 11.3 mg/m3 (DM catchers) and 8.1 mg/m3 (TM catchers). Full-shift dust exposure exceeded the Danish occupational exposure limit (OEL) of 3 mg/m3 for organic dust by at least a factor of 2. From paired personal sampling data the concentration of respirable dust ranged from 18% to 28% of the total dust concentration. The average exposure level to bacterial endotoxin in total dust at 82 ng/m3 for DM catchers and 42 ng/m3 for TM catchers exceeded a limit of 10 ng/m3 recommended for poultry processing industry workers in the United States. Endotoxin content of airborne dust averaged 6.5 +/- 4.9 ng/mg. Exposure to microorganisms was determined by microscopy (total count) and by culturing (viable count). The geometric means for total count (microorganisms/m3) were 7.0 x 10(8) (DM catchers) and 4.9 x 10(8) (TM catchers) and for viable count 3.2 x 10(7) cfu/m3 (DM catchers) and 1.4 x 10(7) cfu/m3 (TM catchers). The ratio of microorganisms counted by microscopy to levels of viable microorganisms ranged from 5 to 200, implying a strong underestimation of exposure levels from viable counts alone. It was concluded that Danish chicken catchers were exposed beyond recommended limits for the air contaminants evaluated.(ABSTRACT TRUNCATED AT 250 WORDS)

EXPOSURE ASSESSMENT OF AIRBORNE MICROORGANISMS BY FLUORESCENCE MICROSCOPY AND IMAGE PROCESSING

The purpose of this study was to improve the exposure assessment of airborne microorganisms by means of image processing of fluorescence microscopy images. This technique reduces the analysis time and also offers the opportunity to measure the size distribution of the microorganisms. We developed and implemented an automatic focusing procedure in order to count and size evaluate the microorganisms in the sample. However, automatic focusing was not possible if there were any impurities such as larger particles present. Therefore, manual focusing of the microscope had to be applied in connection with automatic counting and size evaluation when assessing the exposure of workers handling materials containing microorganisms, for example. This is also an improvement as it is faster than the fully manual standard methods. The new methods developed in this study correlated (r2 > 0.85) with the standard method for samples of E. coli and for samples of generated airborne bioaerosols from household waste, although a correction factor is necessary. No correlation was found for samples of generated bioaerosols from composted waste. This work has established a possibility for improving exposure assessment of airborne microorganisms by means of image processing instead of manual counting.

Occupational exposures and health among Danish farmers working in swine confinement buildings

Abstract In a cross-sectional study at 11 large pig-breeding farms various work-related exposures were measured. The purpose was to record several simultaneous exposures in relation to various work tasks. The concentration of total dust and respirable dust was 4.13 mg/m3 and 0.48 mg/m3 respectively. For all farmers the relative heart rate increase during work was 29% of maximal work capacity ( ±9.7% ), indicating a high work load. Increased pulmonary ventilation causes a higher risk for deposition of dust in the airways. The total tonnage lifted per day was 4,725 kg and was considered to be high according to Danish guidelines. During 40% of the working time, the work was performed with a forward flexion of the back of more than 20°. The load on the back may be the cause of the high one-year prevalence of low back pain at 62%. The work task of feeding pigs was the task with the highest number of simultaneous exposures.

Microorganisms and endotoxin in stored biowaste percolate and aerosols

Source separated biowaste was stored in containers at temper atures ranging from 16°C to 29°C in a climate chamber for two weeks, simulating outdoor storage in a domestic waste collec tion system. Samples of exuded percolate were collected after 3, 4, 6, 8, 10, 12 and 14 days and analyzed for content of micro organisms and endotoxin. Throughout the storage period, the mean concentrations (GM) of total microorganisms ranged from 5.0 to 12 × 109 cells ml-1 and concentrations of endotoxin were between 0.54 and 1.5 × 106 EU ml-1 (45 to 130 ug ml-1). The maximum levels of microorganisms and endotoxin in the percolate were stable during storage and no significant differ ence was found between storage times of one or two weeks, which corresponds to common Danish collection frequencies of biowaste. Analyses of the microflora indicated dominance of bacteria as demonstrated by almost equal concentrations obtained by aerobic and anaerobic cultivation (2.8 to 9.0 × 108 and 3.1 to 12 × 10 8 cfu ml-1, respectively). Yeasts formed a minor part of the microflora (below 0.5% of the total number of microorganisms) and molds were only detected sporadically at concentrations close to the limit of detection. For percolate keeping a pH below 5 during the first week of storage, a ten dency (p = 0.08) was observed towards lower concentrations of aerobic Gram-negative bacteria and yeasts as compared to per colate exceeding a pH of 5. In two weeks, a mass of 17 kg of bio waste exuded approximately 1.31 of percolate (range: 0.7 to 2.1 1), and handling experiments demonstrated that bioaerosols generated from splashing percolate may cause exposure risks of endotoxin and microorganisms. Bioaerosols above stored bio waste contained fungal spores up to 1.8 × 104 cfu m-3 but no detectable bacteria and endotoxin. Headspace measurements of gases showed maximum emission of hydrogen sulfide and methyl mercaptan after one week of storage, while concentra tions of ammonia increased throughout the two week storage period.

Experimental generation of organic dust from compostable household waste

The objective was to assess the influence of different waste storage systems on the emission of bioaerosols and gases from compostable household waste. Batches of waste were stored for 14 days in different storage systems: ventilated containers (compostainers) with or without added structure material and closed containers with or without a preservation additive. The microbial potential of the waste was measured with a rotating drum after storage. The weight loss in the compostainers (39%) was higher than in the closed containers (9%). Hydrogen sulphide and mercaptans developed in the closed container, and the concentration of ammonia increased continuously in both systems to 140 ppm. The microbial content for the incubated waste was high for closed containers compared to compostainers, and waste in closed containers generated a liquid rich in endotoxin and bacteria. The aerosols emitted from the waste consisted mainly of fungal spores, especially Aspergillus fumigatus, and no significant differences were observed between the systems. The endotoxin potential was high for waste stored in closed containers. The use of a preservative prevented microbial growth and reduced the emission of bioaerosols and gases substantially.