Exposure to dangerous substances in the waste management sector

The amount of waste generated in the EU has been growing and new waste handling processes have emerged in the waste management sector. Workers in the waste management sector may be exposed to biological and chemical risks such as vapours, smoke, fumes and dust as well and they may also need to handle chemical substances and infectious materials. According to interviews and follow-up studies workers in this sector have been found to experience more work-related symptoms and illnesses than other occupational groups ^[1], ^[2]. For example the work conducted in composting of waste facilities is associated with adverse acute and chronic respiratory health effects in the workers, such as mucosal membrane irritation, chronic bronchitis, conjunctivitis, and an accelerated decline of lung function. Workers may be exposed if they inhale hazardous substances, present in complex mixtures of aerosols, bioaerosols and volatile organic compounds produced during the treatment of domestic, medical and industrial waste. They may also be exposed through direct contact (with skin or eyes or via the mouth) to hazardous chemicals, dust, and microorganisms present in the waste material. The following article provides information on the safe handling of dangerous waste, including how to avoid biological and chemical health risks.

Occurrence of biological hazards

Waste handling and treatment activities are generally diverse in nature. The enterprises in the sector may include recycling plants for paper, glass, synthetic and wrapping materials, composting plants, landfills and sewage plants. Evidently the activities and materials involved can also be diverse, resulting in a complex exposure situation of workers to multiple biological agents including infectious pathogens as well as to non-infectious bioaerosols containing fungi, bacteria, mycotoxins, endotoxins and glucans. For example, workers in landfill sites may potentially be exposed to high levels of bioaerosols during the dumping of waste. During sorting activities of recycled materials the exposures may vary depending on the exact composition of the handled waste. Waste materials contain nutrients and they often are moist, thus providing a favourable environment in which microorganisms can thrive. The age and composition of waste together with storage temperature and humidity affect both the type and quantity of microorganisms as well as their ability to live and multiply in the waste. Also, the development of biodegradable waste recycling leads to increasing amounts of decaying organic materials being handled and some processes, such as composting, encourage the growth of microorganisms in the biodegradable waste fraction^[3].

Medical and clinical waste or the waste derived from animal origins may well contain pathogenic microorganisms, i.e. these biological agents pose a risk of infection. Many of these pathogens have been categorised into four groups based on their relative risk in a European Directive 2000/54/EC for biological agents ^[4]. However, the greatest work-related hazard is usually attributed to irritation of the mucous membrane and to toxic or allergenic effects experienced after inhalation of a large number of microorganisms and their fragments ^[5]. These are invisible and they do not necessarily even smell.

Bacteria and their fragments

Biowastes, especially food scraps very often contain huge numbers of bacteria. Most of these bacteria are saprophytic bacteria, i.e. they feed and grow on decaying organic matter. However, some of these species particularly those present in animal waste, may be pathogens, and they can cause serious infections, such as brucellosis (Brucella spp.), campylobacteriosis (Campylobacter spp.), listeriosis (Listeria monocytogenes), salmonellosis (Salmonella spp.), shigellosis (Shigella spp.), and yersiniosis (Yersinia spp.).

All gram-negative bacteria in the waste contain components called endotoxins, which is a constituent of their cell walls. Endotoxins are pulmonary immunotoxicants ^[6]. They can cause acute systemic (fever, shivering, and joint pain) and respiratory symptoms (dry cough, shortness of breath), as well as acute lung function changes. One chronic effect of endotoxin exposure is an accelerated decline in lung function (leading to COPD, chronic obstructive pulmonary disease). Additionally, endotoxins may lead to side effects in the way a person responds to allergens since they may synergistically enhance the release of allergic mediators and increase the production of antibodies.

Gram-positive bacteria, such as Actinobacteria, Bacillus, and Clostridium genera, produce spores which are difficult to destroy. They can be resistant to heat, cold, desiccation and sunlight and hence, these types of bacteria may also survive in bioaerosols. In particular, Thermophilic Actinobacteria can promote the development of extrinsic allergic alveolitis. Bacillus and Clostridium bacteria may be considered as pathogens, since, in some circumstances they can be the source of anthrax (caused by Bacillus anthracis), botulism (toxin of Clostridium botulinum), or tetanus (Clostridium tetani).

Fungi and their spores and mycotoxins

Fungi, such as moulds and yeasts, may trigger extrinsic allergic alveolitis, asthma and hypersensitivity, or organic dust toxic syndrome (ODTS) a property they share with bacteria ^[5]. Extrinsic allergic alveolitis (sometimes called hypersensitive pneumonitis) consists of a range of symptoms, including influenza-like symptoms, chills, fever, chest tightness, dry cough, malaise, weight loss, muscle and joint pains. The acute symptoms of allergic alveolitis appear 4 to 6 hours after exposure to the microorganisms. ODTS is an acute condition; it is the body’s response to exposure to toxic levels of a hazard. The symptoms are similar to those caused by allergic alveolitis, but in general, ODTS does not lead to long term health effects and usually disappears on the next day after the exposure.

A fungus Aspergillus fumigatus can also cause infectious mycosis (broncho-pulmonary aspergillosis). Immuno-compromised individuals are at a particular risk of suffering severe symptoms. Some fungal species, such as Alternaria and Cladosporium, are also known to be producers of type I allergens, which cause hypersensitivity reactions such as allergic rhinitis as an allergic reaction. Prolonged exposure to bioaerosols is likely to give rise to an increased risk of sensitisation to common fungi. Workers who have previously been sensitised to moulds may also subsequently experience an exacerbation of symptoms at very low exposure levels.

Mycotoxins, secondary metabolites of fungi, are known to be potent carcinogens and some are classified as carcinogenic to humans (group 1) by the International Agency for Research on Cancer (IARC)^[3]. However, very little is known about the respiratory health effects attributable to occupational airborne exposure to mycotoxins.

Viruses and prions

Medical and clinical laboratory waste may include extremely infectious agents, e.g. hepatitis, HIV and haemorrhagic viruses and prions but contaminated waste might also be present in domestic or industrial waste. Workers’ exposure to these infectious viruses occurs mainly through accidental contact with a sharp object, for instance when collecting or separating waste. Not only needles but also glass and cans pose a risk^[7]. However, little is known about the potential risks that workers incur through exposure to viruses and prions present in the air or on surfaces of waste materials being processed.

Parasites and vector-borne diseases

“Vector-borne disease" is the term commonly used to describe an illness caused by an infectious microbe that is transmitted to humans by blood-sucking arthropods. A vector may also be an animal, such as a rodent or a cat that is harbouring disease-causing microorganisms allowing them to transfer from one host to another. These kinds of vector-borne diseases include leptospirosis (Leptospira spp.), Q fever (Coxiella burnetii) and toxoplasmosis (Toxoplasma gondii). ^[8] Waste can also include the eggs of parasitic worms (helminths e.g. Ascaris lumbricoides) and the cysts of parasites which can cause a gastrointestinal infections such as amoebiasis (Entamoeba histolytica), and giardiasis (Giardia lamblia).

Allergens

Contact with the organic components of animal or vegetable waste may have impacts on workers through allergenic routes. The allergic type I responses are generated by immunological sensitisation towards a specific agent and they lead to the production of a specific immunoglobin E response. Some typical IgE-mediated allergies include asthma, allergic rhinitis and dermatitis caused by a skin contact with the allergen.

Routes of entry for biological agents

Biological hazards are derived from microorganisms entering the host and then propagating within the body, resulting in disease. The most common routes of entry for biological hazards are through direct contact with waste or inhalation of airborne microorganisms and their fragments. Direct contact can involve absorption through mucous membranes (eyes, nose and mouth) or damaged, burned areas where the skin is not intact. Ingestion during eating and smoking is also possible if the hands are contaminated with waste materials.

There is little data on the dose-response relationship between exposure and symptoms. The response due to a microorganism depends on its virulence, infectivity, and the resistance of the body. Thus there may be great difficulty in determining limit values to which the health effects can be attributed. The general consensus is that exposure to high concentrations of microorganisms should be avoided. Prolonged exposure to elevated levels significantly increases the risk of disease. Respiratory effects can be traced to the physical size and ability of the microorganisms and their fragments to be inhaled deeply within the respiratory tract.

Chemical agents in the waste management sector may be inherent to the waste itself and/or produced during waste treatment. Workers may be exposed to dangerous chemical substances in waste treatment activities and different kind of health risks have been described ^[9].

Hazardous waste from industry and households may contain high amounts of all kinds of chemical substances. If they are not recognised and handled as hazardous waste, this could increase the hazardous properties of municipal solid waste in landfill, or during the incineration or composting plant processes ^[10].

Metals

Heavy metals are known to pose a considerable health risk in the waste management sector. Many industrial products (e.g. batteries, electrical equipment, stainless steel or plastic products) containing heavy metals still end up as waste and are unlikely to be recycled properly. Heavy metals might also be released during the waste processing. Currently it is still difficult to identify the actual sources of heavy metals detected in different waste types and products (e.g. lead in flue gas in incinerators may have originated from lead pigments in plastic or lead batteries)^[11].

Waste management workers face health risks if they are exposed to metals during collecting and handling of toxic waste and during waste incineration processes. More than 30 different metals have been detected in the incinerated ash of unsorted urban waste, and most of these metals, such as arsenic, cadmium, chromium, lead, and mercury, are harmful to human health. In addition, many of these metals have an accumulated effect ^[12]. Workers may be exposed to metals by inhalation or ingestion or through skin contact. ^[13].

Arsenic

Arsenic in waste typically originates from industrial products, such as wood preservatives, paints, dyes, and semiconductors. In addition, arsenic may be released during the burning of fossil fuels and wastes. One of the most dangerous sources of inorganic arsenic is the incorrect disposal of electronic waste ^[14].

Arsenic is classified as being toxic if swallowed (H301) or inhaled (H331) ^[15]. It may exert detrimental effects on skin, mucous membranes and the nervous system. The effects may be delayed, and repeated or prolonged exposure of arsenic may cause damage to skin and the peripheral blood vessels. In addition, increased incidence of hypertension, cardiovascular disease and diabetes have been reported. Arsenic iscarcinogenic to humans and possibly is dangerous toxicity forhuman reproduction or development ^[13], ^[16].

Cadmium

The use of cadmium has been restricted in electrical and electronic equipment in the EU countries since 2006 based on directive 2002/95/EC ^[17]. This directive has since been repealed and replaced by directive 2011/65/EU ^[18]. However, cadmium found in waste incineration plants might originate from pigments and stabilisers in plastic or possibly from steel plating ^[11].

Cadmium is a heavy metal which is lethal if inhaled in sufficient quantities (H330) but it also damages organs if there is prolonged or repeated exposure (H372). It may cause cancer (H350) and it is suspected of causing genetic defects (H341) as well as damaging fertility and the unborn child (H361fd) ^{[15] [19]}. Cadmium fumes are irritating to the respiratory tract and may cause acute lung oedema and metal fume fever. The effects may be delayed and during repeated or prolonged exposure to dust particles, the lungs may be affected. Cadmium may have effects on the kidneys, such as causing kidney impairment ^{[13] [16]}. Workers may be exposed during waste treatment procedures.

Chromium

Chromium is used in tanning, wood preservation, and it can be present in pigments and dyes for plastics, paints, and textiles. Chromium alloys in stainless steel are an application. Today, most of chromium alloy products are collected for recycling. However, many types of stainless steel are not magnetic and they cannot be separated from waste streams by magnetic separation. Thus stainless steel may end up reaching solid waste incinerators or especially landfills, if collection for recycling is not carried out properly ^[11].

Chromium may cause irritation and corrosion of skin and mucous membranes tissue in nose and throat; it can also damage kidneys, blood, and liver. An allergic skin reaction (H317) may be caused by exposure to chromium (especially Cr(VI)) compounds in the working environment. Chromium compounds are also believed to cause cancer if they are inhaled (H350i). ^{[13] [15] [16] [19]}

Lead

Many different lead containing products end up in waste management systems and can contaminate incineration plants or landfills. Lead is still used in many products, such as plastics, lead crystal glass, cathode ray tubes, ceramics, solders, and pieces of lead flashing.

Lead can exert effects on the blood, bone marrow, central and peripheral nervous systems, gastrointestinal tract and kidney. In addition, lead and lead compounds may damage the unborn child and they are suspected of damaging fertility (H360Df). Lead is probably carcinogenic to humans. ^{[13] [15] [16] [19]} Lead compounds may damage many organs if there is prolonged or repeated exposure (H373) and they are harmful if swallowed (H302) and inhaled (H332). ^[15]

Mercury

The principal mercury sources in waste are dental amalgam, thermometers, batteries, backlights of computer screens, and fluorescent lights ^[11]. Volatile mercury which can react to form toxic organic compounds is one of the most harmful metals present in waste. Mercury is irritating to the skin and organic mercury compounds can be fatal if they come into contact with skin (H310) or if swallowed (H300). High levels of mercury vapour can cause pneumonitis and symptoms in the kidneys and central nervous system, even long after the actual exposure (H372, cause damage to organs through prolonged or repeated exposure). Mercury is suspected of being able to impair fertility and it may damage the unborn child (H360D). ^{[13] [15] [16]}

Gases

Ammonia

Ammonia is a colourless, pungent odour gas, that may be released into the environment during the natural breakdown of organic matter. Ammonia can be released from waste disposal sites where workers may become exposed to ammonia through inhalation or contact with the skin. Ammonia is irritating to eyes, skin, and respiratory tract (H314). Inhaling high concentrations of ammonia may cause lung oedema (H331) and frostbite. ^{[13] [15] [16] [20]}

Nitric oxide, nitrogen dioxide and nitrous oxide

Nitric oxide, nitrogen dioxide and nitrous oxide can be released during energy production processes, including waste incineration. Workers may be exposed to these nitric compounds by inhalation. Nitric oxide may also exert effects if it comes into contact with the skin.

The effects of nitric oxide and nitrogen dioxide may be delayed. Nitric oxide is irritating to eyes and respiratory tract. Inhalation of nitric oxide may cause lung oedema and it has detrimental effects on blood. These effects may be delayed, repeated or prolonged exposure may affect the lungs. ^[13]

Nitrogen dioxide is corrosive if it comes into contact with the skin or respiratory tract (H314), and inhalation of the gas or the vapour may cause lung oedema (H330)^[15]. Long-term or repeated exposure may have effects on immune system and pulmonary tissue resulting in decreased resistance to infection. In addition, nitrogen dioxide possibly exerts toxic effects upon human reproduction. ^[13]

Nitrous oxide may alter the activity of the central nervous system, and with prolonged or repeated exposure may have effects on bone marrow and the peripheral nervous system. This substance may also cause reproductive toxicity in humans. In a liquid form, nitrous oxide may cause frostbite. ^[13]

Sulphur dioxide

Sulphur dioxide is formed during incineration processes, such as waste combustion. Sulphur dioxide is a colourless gas, which irritates the eyes and respiratory tract. It can cause severe superficial burns and eye damage (H314). Inhalation may cause asthma-like reactions and repeated or prolonged inhalation exposure may trigger asthmatic attacks (H331). ^[15] This substance may cause frostbite if a worker comes into contacted with its liquid form.

Reduced sulphuric compounds

Reduced sulphuric compounds, such as hydrogen sulphide, dimethyl sulphide, or methyl mercaptan can be formed in waste dumps and composts that have been poorly ventilated. In addition to their unpleasant smell, inhalation of reduced sulphur-containing compounds causes serious health effects even in small concentrations. Exposure to sulphuric compounds prevents the energy metabolism and thus is very harmful, especially to tissues which have large energy demands, e.g. brains, kidneys, and heart.

Hydrogen sulphide can irritate the eyes and respiratory tract, and it may impair the activity of the nervous system. Inhalation of the gas can cause lung oedema (H330) and the liquid form may cause frostbite, though these effects may be delayed ^[15]. Dimethyl sulphide is irritating to eyes and skin and it can potentially to be neurotoxin. Methyl mercaptan is toxic if inhaled (H331) and it irritates eyes and respiratory tract and it may exert central nervous system effects. The effects may be delayed as well. ^{[13] [15] [16]}

Other gases in waste management

Methane gas and carbon dioxide have been identified as the primary health hazards present in landfill sites. High methane concentrations in the air cause permanent damage to health, because they prevent tissues from obtaining oxygen. Carbon dioxide acts on the respiratory tract and central nervous system. It can cause frostbite, and prolonged or repeated exposure may have metabolism consequences ^[16]. Carbon monoxide might be a problem in composting plants and, in addition, it can also be present indiesel exhaust ^[9]. It is toxic if inhaled (H331) and may exert effects on blood, and the cardiovascular and central nervous systems (H372). It is suspected of damaging fertility and it may damage the unborn child (H360D). ^{[13] [15] [16]}

Volatile organic compounds

In the waste management sector, volatile organic compounds (VOCs) can be released directly from waste materials or they are released due to metabolic activity of microorganisms. The health effects of volatile organic compounds are typically evaluated by total amount of these compounds. Even low concentrations of VOCs may cause acute health effects most commonly to the eyes and respiratory tract. A mixture of VOCs has been found to cause irritation in the respiratory tract and inflammatory responses in the upper airways ^[9]. However, workers in waste management can be exposed to some VOCs also through skin contact. Many of the volatile organic compounds, e.g. benzene, toluene, dichloromethane, tetrachloroethylene, trichloroethylene, dichloroethane, phthalates, butadiene and dimethylacetamide found in waste arecarcinogenic, mutagenic and reprotoxic (CMR chemicals).

Other chemical compounds

Polychlorinated dibenzo-p-dioxins (dioxins) and polychlorinated dibenzofurans (furans) are well known pollutants, and these are produced during waste incineration at temperatures below 800 °C, or when combustion is incomplete, or if polyvinyl chloride (PVC) plastics are incinerated. The health effects of dioxins and furans are, known to cause impairment of the immune system and the development of nervous system as well as reproductive functions. Dioxins are classified as a known human carcinogen. Furthermore, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can cause allergic dermatitis, chloracne and gastrointestinal disturbances. ^{[9] [13] [19]}

Polychlorinated biphenyls (PCB) can be considered as a problem in waste management for the same reasons as dioxins and furans, or when handling PCB containing waste ^[9]. It is known that PCB compounds may cause chloracne, liver damage, and reproductive effects, and they increase the risk for cancer. ^[13]

Polyaromatic hydrocarbons (PAH) are formed during all kinds of incomplete combustions. Most PAH compounds are carcinogenic and mutagenic. For example, naphthalene is a PAH compounds. Acute exposure to naphthalene by inhalation or by dermal contact has been reported to cause haemolytic anaemia and to damage the liver. It may be a reproductive poison and possibly it is also carcinogenic. ^[13]

Workers in waste management are also exposed to high levels of dust. Small particles are most harmful because they can penetrate deep into the respiratory tract, even as far as the alveoli. Elevated concentrations of particles might increase the likelihood of an asthmatic attack, impairing pulmonary capacity and increasing respiratory inflammation. ^[9]

Asbestos

Several naturally occurring fibrous silicate minerals are called asbestos. They are characterised by their separate advantageous thin, durable threads.Asbestos was once widely used because of its properties: it is heat resistant, withstands attacks from acids and other chemicals, is a good insulator, has a high strength and can be woven. Nowadays the use of asbestos is forbidden. From 2005 onwards all types of utilization of asbestos were banned in the EU based on the directive 1999/77/EC^[21]. This restriction is now part of the REACH regulation^[22] (entry 6 of annex VII) and the manufacture, selling and use of asbestos fibres and products containing these fibres is prohibited. However, asbestos is still present in many buildings and other structures. Building maintenance workers and workers in the waste management sector (e.g. handling demolition waste) are at a high risk of coming into contact with the fibres^[23]. The protection of workers from exposure to asbestos is regulated by directive 2009/148/EC, which replaces previous Directives, incl. directive 83/477/EEC ^[24].

Depending on the type of the fibres and the level and duration of exposure, asbestos exposure can lead to asbestosis, a chronic lung disease causing shortness of breath, coughing, and permanent lung damage and lung cancer. A smoker is 50 times more likely to develop lung cancer than a non-smoker if exposed to asbestos. There is no known safe level of exposure to asbestos. The time between exposure to asbestos and the first signs of disease can be as long as 30 years ^[25].

Other mineral dusts

Workers in the waste management sector may also be exposed to other mineral dusts. Crystalline silica is one such mineral dust and it is a basic component of soil, sand, granite, and many other minerals. Quartz is the most common form of crystalline silica. Crystalline silica has been classified as a human lung carcinogen and all work involving exposure to respirable crystalline silica dust generated by a work process is listed as a carcinogenic in the EU Directive 2004/37/EC - carcinogens or mutagens at work^[26]. Additionally, breathing in crystalline silica dust can cause silicosis a lung disease marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. Smoking is known to cause lung damage and it adds to the damage caused by breathing in silica dust ^{[27] [28]}.

Man-made mineral fibres

Man-made mineral fibres (MMMF) do not occur in nature. Man-made mineral fibers are produced using inorganic materials and are widely used as thermal and acoustic insulation. These basically include continuous fiberglass filaments, glass wool (fiberglass insulation), stone wool, slag wool and refractory ceramic fibers. The significant commercial production of man-made mineral fibres began in the early twentieth century. MMMF products can release airborne respirable fibres during their production, use and removal. MMMF may irritate eyes, skin and the respiratory tract. Prolonged exposure to these fibres could lead to long-term effects, and some types of mineral wool are considered as possibly carcinogenic to humans, similar to asbestos. This effect may depend upon the properties of the fibres, i.e. their diameter and length, chemical composition and persistence within the body ^[19], ^[29].

Wood dust

Airborne wood particles and wood dust from materials made from wood e.g. building materials in waste processes present a potential health problem. Inhalation of these particles may cause skin disorders, obstruction in the nose, and rhinitis, asthma and a rare type of nasal cancer. The extent of these risks depending on different wood types has not been clearly established ^{[19] [30]}.

Nanomaterials

Nanomaterials, also called nanoparticles or ultrafine particles, possess unique chemical, physical and mechanical properties, and therefore they are incorporated into a wide variety of applications in different industrial branches, ranging from food and feed products to transport-related equipment. New sophisticated multicomponent or hybrid materials are being designed at an accelerated pace. Developing these innovative materials is an important driver for European competitiveness, but the increased use of nanomaterials also means that an increasing number of workers are potentially exposed at every stage of the material’s life cycle, from research and development through production to disposal and waste treatment.

Nanomaterials may have very different health hazards from the same substance in larger size particles. The health effects of nanomaterials are mostly based on animal (in vivo and cells) laboratory studies, but some epidemiological and toxicological studies are also available. Exposure to ultrafine particles like diesel exhaust has been claimed to be linked to higher mortality and aggravation of asthma and lung cancer. Metal oxide fumes may lead to so-called metal fume fever, which is an influenza-like disease. Nanomaterials have also been linked many other symptoms, e.g. cardiovascular effects, pulmonary effects, dermal toxicity as well as cytotoxicity and oxidative stress of cells ^{[31] [32] [33] [34]}.

Collection, sorting and recycling of waste, disposal to landfill

During collecting of waste and when working in landfills workers are exposed to high levels of dust, that may contain bioaerosols, asbestos, crystalline silica, man-made mineral fibres, nanoparticles and metals. Bioaerosols, i.e. airborne particulate matter associated with microorganisms and their fragments, are generated by physical handling of waste in a number of ways. Different processes, such as shredding and crushing of waste, may be significant sources of airborne particles and bioaerosols. Particularly high levels of bioaerosols may be emitted from the prolonged storage of waste. During handling operations, such as manual waste sorting and recycling facilities, workers can also be injured by materials contaminated by microorganisms. Exposure to bioaerosols during waste collection and landfills depends on which microorganisms are present in the waste, the type of container and machinery e.g. truck, working methods and weather conditions.

Workers may be exposed to metals during collecting and handling of toxic waste. For instance, it is possible to be exposed to lead, mercury, and cadmium when recycling batteries. Exposure to chromium may take place when a worker handles materials during their recycling. Exposure to harmful chemicals may occur directly via recycling or in an indirect manner. For example, potential exposures to electronic waste (e-waste) involves the original constituents of the equipment, substances added (for example acids for chemical stripping of precious metals) during the recovery process, and substances formed as a result of the recycling process itself. The incorrect disposal of e-waste constitutes one of the most dangerous sources of inorganic arsenic entering the environment.

Products made from recycled waste might also contain harmful chemicals. Volatile organic compounds can be released into the air during waste processing and include some badly smelling compounds, carbon dioxide, methane and aromatic and chlorinated hydrocarbons. Ammonia and reduced sulphuric compounds may be produced from waste in landfills. Up to 110 different volatile organic compounds (VOCs) have been detected during waste management processes. Dioxins, furans and PCBs might also be a problem ^[9].

Wastewater treatment

Workers in wastewater treatment have a high risk of contracting a disease as a result of exposure to biological agents. Sewage and unstable sludge contain various pathogens such as viruses, bacteria, and human and animal parasites. These microorganisms can be transmitted to the ambient air in wastewater droplets, which are generated during aeration or mechanical moving of the sewage^[7]. Workers also are at risk of exposure to a variety of chemicals used in wastewater treatment, for example oxidizing agents (chlorine, chlorine-dioxide, hypochlorite, ozone, etc.), strong acids and alkalis, sedimentation or flotation aids, etc. ^[35].

Composting plants

It is difficult to control and prevent the spread of biological agents into air from the biomass present in a composting plant, and therefore high levels of biological agents are present in the ambient air. Different microorganisms react differently to the conditions during composting. Enteric bacteria and viruses are likely to be killed by the temperature and low moisture, but some fungi can proliferate in the warm moist stage and then form spores once the composted waste dries out. Sporulating bacteria may also survive in the composting process as heat resistant spores. Prior treatment of waste, turning of compost piles and sieving of the final outcome of the compost are the most hazardous stages in processing, where compost workers handling the compost are often exposed to high levels of various aerosols and particles ^[9].

Elevated levels of gaseous substances, such as ammonia, VOCs, nitrogen dioxide, sulphur dioxide, hydrogen sulphide and other reduced sulphuric compounds, may also be detected inside of waste treatment plants. The gases are primarily produced by microbes in the decaying organic waste mass. Nitrogen dioxide may originate from the exhaust emissions of machinery.

Bioenergy producing facilities

Bioenergy is renewable energy produced from materials derived from biological sources (e.g. using anaerobic digestion) ^[36]. As a fuel it may include biowaste consisting of wood, straw, manure, sugarcane, and many other byproducts from a variety of agricultural processes. The highest exposure to biological and chemical substances occurs during waste reception and handling before treatment. Elevated concentrations of hazardous substances may also occur during the opening process, especially in areas with enclosed tanks or lines. If gases are able to leak from the digester,ignition and explosion associated with methane and hydrogen are the main risks.

Incineration

Workers may be exposed to smokes and gases in waste incineration process. Bioaerosols can be present in waste reception and storage. There may be significant exposure to heavy metals, quartz, dioxins, furans, PAH compounds and solvents when handling combustion ash and during cleaning andmaintenance operations. These areosols can bind to solid particles. Nitric oxide, nitrogen dioxide and nitrous oxide can also be released from energy production process and also from waste incineration. Dioxins and furans as well as PCBs and PAHs are well known pollutants, that might be produced as waste combustion by-products ^{[9] [36]}.

Workers should be protected against risk of harmful substances since there are both national and EU legislations regulating worker safety. OSH legislation is aimed at protecting workers from safety and health risks in general and of chemical substances and biological agents in the workplace. The OSH framework directive 89/391/EEC^[37] lays down the general requirements and determines that employers should assess the safety and health risks and take adequate measures. Directive 2000/54/EC on the protection of workers from risks related to exposure to biological agents^[4] at work aims to minimise the health risks from biological agents in the workplace. Directive 98/24/EC on chemical agents at work^[1] and directive 2004/37/EC on carcinogens or mutagens at work^[26] aim to reduce the exposure of workers to dangerous substances in workplaces. All these OSH directives require employers to carry out a workplace risk assessment of the safety and health risks, including the risks from exposure to biological agents and dangerous substances, and to set appropriate protection and prevention measures^[2]. Occupational exposure limits (OELs) represent an important tool for risk assessment and management. Some of the OELs of hazardous substances in waste management sector are presented in table 1. No legally binding limits for bioaerosols have been established. A health-based recommended OEL (8-hour TWA) for endotoxin could be 90 EU/m³ (9 ng/m³), because no adverse health effects are expected to occur after chronic occupational exposure below that level ^[6].

Table 1 – Some of the harmful compounds found in the waste management

*an OEL is mentioned if it is available based on EU-legislation.

Source: Adapted from Gestis Substance Database ^[13]

Apart from the OSH legislation aimed at protecting workers, there are EU legislative acts regulating the management and reduction of waste. The Waste Framework Directive 2008/98/EC^[40] is the key legislative document on waste at the EU level. The directive lays down measures to protect the environment and human health by preventing or reducing the adverse impacts of the generation and management of waste and by reducing overall impacts of resource use and improving the efficiency of such use. Waste is defined as any substance or object which the holder discards or intends or is required to discard. The directive also defines hazardous waste as waste that displays one or more of the hazardous properties as listed in annex III of the directive. The hazardous properties are classified into 15 categories (table 2). Commission Decision 2000/532/EC^[41] on the list of waste provides further provisions for the assessment of hazardous properties and the classification of waste. It provides the list of wastes, categorised into chapters, sub-chapters and entries. More information on the classification of waste is available in technical guidance from the EU Commission. Provisions of the waste framework directive state that member states must take measures for managing hazardous waste (ban on the mixing of hazardous waste, separate collection, permit systems for collecting and treatment, etc.). A complete overview of legislative acts on waste management is available at the EUR-Lex website.

Table 2 - Properties of waste that render it hazardous (waste framework directive 2008/98/EC, annex III)

At first an inventory of the chemical and biological substances in the waste management processes has to be made in the workplace. In addition, dangerous substances generated by the process, such as dusts, fumes and aerosols, have to be taken into account. Identifying dangerous substances in the waste management processes is very challenging because of the lack of labelling and the lack of safety data sheets on many of the substances present in the waste. Even though it presents a challenge, it is important to assess the potential exposure to the identified dangerous substances, examining the type of compounds and their potential hazardousness, intensity, length, frequency and occurrence of exposure to workers. Measurements can be carried out if needed to determine the level of exposure. The severity of the established risks should be ranked. The ranking list can then be used to draw up an action plan to protect workers. If a hazardous chemical is known to be present in the waste collection, then it is important to gather as much information as possible about the hazards and the prevention measures needed. It should be noted that the CLP and REACH regulations do not cover hazardous waste and the obligations regarding labelling, packaging as well as information (Safety Data Sheet) do not apply to waste. However, information about chemical substances generated and communicated in the framework of REACH holds relevant information for taking adequate measures. Furthermore, the classification of hazardous waste (see table 2) is based on the CLP-classification and therefore also useful for determining the associated risks and measures.

Substitution and elimination

Exposure in the waste management sector can be prevented if one is able to avoid the dangerous substances in products that end up in the waste. If not possible, then the forming of hazardous waste should be eliminated. For example, according to EU Directive Exposure 2011/65/EU the use of certain hazardous substances in electrical and electronic equipment is restricted ^[18]. In addition, in order to prevent the generation of hazardous waste, the Directive requires the substitution of various heavy metals (lead, mercury, cadmium and hexavalent chromium) and brominated flame retardants – polybrominated biphenyls (PBB) or polybrominated diphenyl ethers (PBDE). Hazardous substances should also be avoided when substituting hazardous products for safer ones, such as using water based paints instead of their solvent-based counterparts. Optimisation of the composting process and gas treatment with biofiltration can reduce VOC emission levels as well as the concentration of ammonia and other odorous compounds in composting plants.

The formation of dioxins and furans can be reduced by optimising the incineration process. ^[1] In the disposal of biological hazards such as medical and clinical waste, it is important to store them into spill-proof containers. The safe packaging, labelling and documentation requirements for infectious substances are described in the guidelines of the World Health Organisation ^{[42] [43]}. Diseases-carrying vectors such as rodents have to be kept away from waste by keeping it in closed bins. Avoiding long storage times of wastes and their storage in dry and cold circumstances prevent the multiplication of microorganisms in the waste. Waste management processes should also be developed in order to minimize the formation of harmful substances.

Isolation

Work processes in waste management should bedesigned in a way that when using adequate equipment and materials, one can reduce workers’ exposure to dangerous substances. Avoiding the generation and release of bioaerosols, dust and gas into the air from waste is an effective prevention measure. ^[1] The risks are likely to be minimal in situations where processes are entirely automated and enclosed. Doors and windows of vehicles must be closed on site. However, maintenance and repair workers may have to enter enclosed spaces and therefore are still at a high risk. Specific measures have to be put in place for these operations.

Ventilation

Effective extraction ventilation of processes, a good supply of fresh air to the workspace, local and general ventilation and working inside a sealed cap with air filtration have a major impact on reducing exposure to hazard airborne substances. A high efficiency particulate air filtration is needed to remove most of the biological agents from the atmosphere in the ventilation systems. Particulate air filtration is also needed to avoid exposure to other dust particles and aerosols. Similar activated carbon filtration systems are available for gases. The regular maintenance of the ventilation systems is essential. ^[1]

Administrative controls

It is difficult to prevent exposure to these hazards completely by elimination and engineering controls. If the exposure is not avoidable, it should be kept to a minimum by limiting the number of exposed workers as well as the exposure time and frequency of the exposure.

Leak detection and preventive measures

The employer has to ensure that regular checks for chemical leaks and spills are conducted. In hazardous places, workers should use gas detectors, which can visibly and audibly alert them in times of danger. Gas detectors can be used to monitor oxygen, toxic and combustible gases and vapours. In combination with an external pump, a gas detector can be adapted to screen closed workspaces before the worker goes there him/herself. This has to be done In particular if there is a confined space entry into tanks and pipelines. Similarly a gas detector mounted on the wall is necessary to alert workers who are moving only temporarily into dangerous areas, such as reception areas of waste. Gas detectors have to be maintained on a regular basis in order to ensure that they are functional when needed. In areas where there is a significant risk of harmful gases being present in the air and an acute health risk, no one should be allowed to work alone without supervision.

Personal hygiene and housekeeping

Some infectious microorganisms can survive on surfaces for extended periods of time. Therefore, regular housekeeping is very important in order to inhibit the growth and spread of microorganisms. Surfaces on the workplaces in the waste management should be designed to be easy to clean and workers should have good facilities for washing. Workers must adhere to good personal hygiene, especially before eating, smoking, and when leaving the workplace, so that the microorganisms and harmful chemicals are unable to be absorbed inside the body or transmitted to another environment on the clothes of contaminated workers. Thus,working clothes and footwear should be stored separately from private clothing (black (contaminated)/white (clean) areas).

Training

Information for workers is required to raise their awareness about the risks and the importance of work safety. Workers have also to be trained for safe working practices. The training should ensure that workers are aware of the risk of exposure and how they can control their exposure to the risk.

Medical surveillance

Waste workers should undergo pre-employment screening and regular health surveillance. Individuals with asthma who are sensitized to A. fumigatus or who have some other respiratory disease or who are immunosuppressed should avoid working with biological waste, unless their exposure to bioaerosols can be controlled ^[44]. Waste-handling workers can be vaccinated against some pathogens ^[45]. Vaccine-preventable diseases are hepatitis A and B or tetanus.

Personal protective equipment

Harmful substances in waste products or their spread in waste management should be reduced by elimination, substitution, collection techniques or actions in working habits. If workers are still exposed this needs to be prevented by using personal protective equipments. In this case, the workers have to be trained in the appropriate use ofpersonal protective equipment.

Respiratory protection

If the risk of exposure to bioaerosols or airborne hazardous chemicals cannot be controlled by more effective preventive measures, respiratory protection equipment (RPE) must be worn. When selecting appropriate RPE, it is important to take into account the risks, the tasks, the work environment and the individual characteristics of the worker. RPE such as facepieces (quarter, half and full-face mask and filtering half mask) must fit well to the face and must not show any leaks. Fit tests can ensure a good fit of the mask to the individual.

Protective clothing

The use of protective coveralls and the services of a work wear laundry company can reduce workers’ exposure to biological and chemical agents in waste management. Leak thickness and resistance to permeation and penetration by biological and chemical substances have to be considered in the selection of protective clothing. The mechanical strength of gloves is very important for manual operation conducted by waste workers to prevent cuts and stings. Similar protection is needed forthe feet against hazardous substances.

It is very important to prevent and control of workers’ exposure in the waste management sector where they are confronted with many potential biological and chemical risks. The exposure to dangerous substances, such as microorganisms, gases and metals, has been associated with a wide range of health effects: acute toxic effects, respiratory symptoms and diseases, infections, allergies and cancer. In particular, knowledge and research are needed about the occupational risks related to waste recycling technologies (e.g. landfill mining) and biowaste treatment (e.g. bioenergy producing facilities).