Household organic waste has been identified as the single component of the current residual waste stream most able to contribute towards meeting increasing waste diversion goals. Municipal waste audits have confirmed that organic waste represents up to 35 per cent of the residual waste stream, precipitating a myriad of organic waste collection and processing pilot projects and fully operational municipal programs.
Municipal waste managers have focused almost exclusively on the social, technological and economic challenges to develop and implement organic waste diversion programs while overlooking the new occupational health risks such programs pose to workers. Such occupational health risks are most pronounced for workers involved in organic waste collection and processing facilities. There are more than just hazards from “sharps” (needles, surgical instruments and broken glassware) to consider. Hazards that workers are exposed to in the collection or separation of organic wastes are in the form of biohazards (or pathogens) such as moulds and fungi, bacteria, viruses and parasites.
Diversion programs that include animal and human wastes (pet feces, soiled diapers and feminine hygiene products) especially pose risks as these waste types expose workers to even more dangerous biohazards.
Biohazards under the microscope
Moulds and fungi are simple plants that feed on the living or dead tissues of animals or plants. Bacteria are microscopic single-celled organisms found in air, water and soil and in living or dead animals and plants. Viruses are micro-organisms that reproduce by coming into contact with living cells. Parasites live in the bodies of plants and animals, including the human digestive system, and reproduce by laying eggs.
Workers are potentially exposed to biohazards through direct contact with organic waste as well as the inhalation of airborne particles. Bioaerosols are airborne particles consisting of or originating from micro-organisms (bacteria, viruses, moulds), or metabolites, toxins or fragments of micro-organisms.
These particles come from a variety of sources that once airborne may adhere to solid or liquid particles in the air and are easily inhaled by workers. Warm, wet organic waste is an ideal medium for the growth and presence of biohazards. Typically, bioaerosols consist of very fine particles measuring less than 20 microns in diameter. Particles less than five microns are respirable and can penetrate deep into the lungs. (See tables.)
The potential for worker exposure varies with the types of collection containers and mode of curbside collection (manual or automatic). Recent studies have shown that the greater amount of manual material handling, the more likely workers will be exposed to biohazards. Generally, there is a greater exposure to biohazards in enclosed processing facilities. (It’s also important to note that diagnosis is challenging as workers sometimes mistake an organic waste-related illness for one acquired outside the workplace and may fail to report disease symptoms to the employer.)
The Ontario Occupational Health and Safety Act and regulations provide almost no direction with the exception of the health care sector to protect workers from biohazards. The most applicable section of the Act is the general duty clause for employers to take “all precautions reasonable in the circumstance s to protect the health and safety of a worker.” The Act also requires employers to develop a written occupational health and safety policy and implementation of that policy through a workplace program.
Since documented precautions for worker safety in handling organic waste are almost non-existent in North America, it’s prudent to consider a combination of possible procedures (some of these adapted from the U.S. Environmental Protection Agency):
If potentially exposed to organic wastes, workers should:
* Wash hands thoroughly with soap and water after contact with organic waste;
* Avoid touching face, mouth, eyes, nose, genitalia, or open sores and cuts while working with organic waste;
* Wash hands before eating, drinking, or smoking and before and after using the bathroom;
* Eat in designated areas away from organic waste -handling activities;
* Not smoke or chew tobacco or gum while working with organic waste;
* Use barriers between skin and surfaces exposed to organic waste;
* Remove excess organic waste from footwear prior to entering a vehicle or a building;
* Keep wounds covered with clean, dry bandages;
* Thoroughly but gently flush eyes with water if organic waste contact eyes;
* Change into clean work clothing on a daily basis and reserve footwear for use at the workplace or during organic waste collection;
* Not wear work clothes home or outside the work environment; and,
* Use gloves to prevent skin abrasion.
Management and worker representatives, in conjunction with a qualified safety and health professional, should determine possible personal protective equipment (PPE) needs and conduct appropriate onsite monitoring to determine which type of PPE (if any) is required. Potential equipment can include: goggles, splash-proof face shields (if there is potential for exposure to spray, high-pressure leaks, or aerosolized biohazards), respirators, liquid-repellent coveralls, and gloves. If respirators are required, respirator-fit training should be provided.
Other helpful measures could include the provision of hand-washing stations with clean water and mild soap readily available, and portable sanitation equipment and products. Vehicle cabs should also be wiped down and cleaned of residual mud (or settled dust) frequently to reduce the potential for exposure. In addition, ensure that all workers are provided and are current on tetanus-diphtheria and hepatitis B & C vaccinations.
THE TYPES OF ORGANISMS PRESENT IN ORGANIC WASTE STREAMS:
Principal Bioaerosols Origins and Associations
Bacteria: Gram negative bacteria (E. coli, Salmonella) thermophilic actinomycetes — Abundant in nature and in humans. Outdoors, they originate in water, soil and plants, and are associated with the presence of humans and animals.
Moulds: Aspergillus fumigatus — Ubiquitous in nature; proliferates well in humid conditions. Aspergillus fumigatus is thermo-tolerant, sometimes pathogenic; it is found on manure, compost, wood, other organic material.
Metabolites and Toxins: Endotoxins, Mycotoxins — Ubiquitous, endotoxins are complexes that are integral parts of the outer membrane of Gram negative bacteria. Their presence is often associated with organic dust. Moulds release mycotoxins (spores and propagules).
Virus: Enteric viruses (Rotavirus and others) — A live host cell is required for a virus to survive, spread and reproduce. It may be spread when droplets from an infected source are released but it may not survive long in the air.
A GENERAL INDICATION OF THE TYPES OF HEALTH PROBLEMS ASSOCIATED WITH EXPOSURE TO VARIOUS ORGANISMS:
Principal Bioaerosols Reported Symptoms and Effects and Exposure Limits
Bacteria: Gram negative bacteria (E. coli, Salmonella) thermophilic actinomycetes — Mucous membrane irritation, gastro-intestinal and respiratory problems (gram negative bacteria and endotoxins), and hypersensitivity pneumonitis (thermophilic actinomycetes). From studies carried out in wastewater treatment plants and composting centres, the following limit for 8 hours of exposure, was suggested for Gram negative bacteria: 103 CFU/m3 of air.
Moulds: Aspergillus fumigatus — Allergic reactions, infections and irritation, toxic syndrome through exposure to organic dusts (ODTS). The nature of the dose-response relationship is not known, nor is the existence of a safe exposure threshold. Concentrations of up to 105 CFU/m3 of Aspergillus fumigatus would not be considered a risk for healthy individuals but one spore could be infectious for immuno-compromised persons.
Metabolites or Toxins:
toxins, Mycotoxins — The effects of endotoxins and their role as a bioaerosol are not well known. Symptoms are a cough, shortness of breath, fever, obstruction and inflammation of the lungs, and gastro-intestinal problems. Since 1999, the ACGIH has recommended the use of REL (Relative Exposure Limit); these limits are 30 times the basic or ambient concentrations. The effects of mycotoxins are not well known. Symptoms are: skin and mucous membrane irritations, dizziness, immuno-supression, headache, nausea, cognitive effects.
Virus: Enteric viruses (Rotavirus and others) — Certain enteric viruses could become airborne and under certain conditions lead to infections in susceptible individuals. The release and transportation of airborne viruses and their potential effects on human health in the context of activities involving the application of biosolids are theoretical and have not been documented.
Adapted from Goyer et al. (2001)
Allin Brady is senior consultant of Help Group Inc., based in Mississauga, Ontario and Robert Cook is executive director of the Ontario Waste Management Association. E-mail Allin at email@example.com and e-mail Robert at firstname.lastname@example.org