Harmful micro-organisms

Construction workers can be exposed to a variety of microorganisms such as parasites, bacteria, viruses, and fungi, including mold. The level of risk depends on the type of micro-organism and the work being done. Harmful microorganisms are especially prevalent after floods and hurricanes as the high moisture levels provide an environment where they thrive.  They can cause an infection if they are breathed in, swallowed, or if they penetrate the skin, and can include some very serious illnesses. Some may in turn cause an allergic reaction or are toxic (they produce a poison). Molds are the most common forms of fungi found on earth and can grow on almost any material, as long as moisture and oxygen are available. For more in depth information on mold, see the Mold Hazardous Substance Portal Page.

How to Recognize Microorganism Hazards

Microorganisms are everywhere, but certain types can cause health issues such as respiratory problems, infections, short and long term illnesses. The level of risk depends on the type of micro-organism and the work being done. Harmful microorganisms can be found in rotting food, sewage, dead animals, animal droppings or on moist surfaces in the form of mold.

Working in post natural disaster environments can raise the risk of coming into contact with harmful microorganisms. Flooding and hurricanes are especially dangerous for the spread of microorganisms and other toxins. Standing water is a breeding ground for bacteria, viruses, and mold. These can become airborne and be inhaled, putting people at risk for lung disease. Where floodwater contains sewage or decaying animal carcasses, infectious disease is of concern. Even when the flooding is due to a fairly clean source, such as rainwater, the growth of these microorganisms can cause allergic reactions in sensitive individuals. Floodwaters often leave a layer of sediment of soil, sewage, and toxic chemicals such as arsenic, chemicals from diesel fuel, heavy metals (lead, cadmium, mercury), pesticides, and other hazards. Take precautions to avoid inhaling or ingesting sediment. Breaks in sewer lines and backed up plumbing are common after natural disasters and can make people sick through skin contact, inhalation, or ingestion. Mosquitoes, flies and other insects can spread these hazards to larger areas.

After natural disasters, homes can be abandoned for long periods of time, leaving them a breeding ground for harmful microorganisms. Damp buildings without adequate ventilation and damp furnishings promote the growth of bacteria, dust mites, cockroaches and mold. High temperatures, high humidity, and lack of air circulation accelerates the growth of microorganisms.

In addition, the time spent in large group housing or camps during an evacuation may increase the risk of spread of infectious diseases such as influenza, pneumonia and tuberculosis, especially in vulnerable people, including children, older adults and people with existing lung diseases.

Some common diseases associated with construction work:

• Legionella from water systems with high temperatures. It is a potentially fatal form of pneumonia with symptoms similar to the flu.

• Anthrax from contaminated land and buildings. Anthrax is a potentially fatal infection that is transmitted from animals to humans. The general risk of getting anthrax is very low.

• Blood borne viruses (BBVs) from needlestick injuries. BBVs are viruses that some people carry in their blood and can be spread from one person to another. Those infected with a BBV may show little or no symptoms of serious disease, but other infected people may be severely ill.

• Hepatitis A from sewage or refurbishment of flood damaged property contaminated with sewage. Hep A is an infection of the liver. Symptoms include: yellowing of the skin and eyes (jaundice), very dark coloured urine and pale faeces,abdominal pain and itchy skin. Symptoms usually last between 2-6 months. In most cases, the liver will make a full recovery

• Psittacosis and Salmonella from bird droppings. Psittacosis is is a rare infectious disease, mainly associated with parrots and other similar species but does affect other birds, including pigeons. Symptoms are commonly a flu-like illness and pneumonia usually appearing 5-19 days after exposure. Salmonella is a bacterial infection that can cause significant diarrhoea.

• Leptospirosis/Weil’s Disease from urine of infected rats. Can enter the body through cuts or the mouth and eyes. The disease starts with flu-like symptoms such as a headache or muscle pains. More severe cases can lead to meningitis, kidney failure and other serious conditions. In rare cases the disease can be fatal.

• Tetanus from contaminated cuts and wounds. Symptoms include muscle spasms and stiffness throughout the body, particularly in the neck, face and jaw (lockjaw). Tetanus can be fatal.

• Aspergillus during demolition and refurbishment. Aspergillus is a fungus that can cause significant health problems when breathed in during certain construction work. It is a mould commonly found in many indoor environments.

Health Effects of Harmful Microorganisms

The health effects of microorganisms vary widely depending on the type, concentration, and how one comes in contact with it. Often cases are mild and temporary, but certain microorganisms can be fatal. Others will lie dormant for long periods of time and not show their health effects until much later in life.

Action Plan to Reduce the Risks of Harmful Microorganisms

Risk assessment: It is important that the potential for the existence of harmful microorganisms be built into any risk assessment based on the nature of the work and the environment in which the work is being done. Research should be done into what diseases are known in the area. Think about limiting the risks before work starts.

Control: Follow the general controls below where a risk remains. You may need additional controls for specific tasks/situations.

• Clothing: Use disposable coveralls, gloves etc where appropriate. This clothing should be kept separate from personal clothing worn outside of work hours. Non-disposable overalls should be replaced when soiled and washed with detergent at a high temperature before being re-used.

• Washing: Wash hands, forearms and face before eating, drinking, smoking, using the telephone, taking medication, inserting contact lenses, etc. Avoid hand-mouth or hand-eye contact when in contaminated areas. Dispose of all contaminated waste safely.

• Breaks: Avoid contamination by taking rest and meal breaks away from the work area. 

• First aid: Make sure first aid equipment is fully stocked / maintained and readily available. Cover existing cuts and grazes. Wash any new cuts or grazes immediately with soap and running water and apply a waterproof dressing.

• Vaccination: There are effective immunizations for some diseases like Hepatitis A, Hepatitis B and Tetanus. A decision to vaccinate will depend on a number of factors. A case-by-case approach should be taken, consider relevant factors including the length of time the work will take, how regularly it is done, the amount of contamination present or if similar work has caused exposure / illness in the past.

• Keep Areas Dry: Eliminate standing water, dry moist items, ventilate.

• Eliminate / limit contact: With sewage, animal feces, dead animals and rotting foods.

• Dust control: Prevent dust getting into the air by wetting down the work area. Consider using plastic sheeting to prevent contamination spreading. Make sure ventilation systems are properly maintained / free from contamination.

• Personal Protective Equipment: The type of PPE necessary will depend on the work being done. Gloves, protective clothing, waterproof footwear, and respirators help reduce contact with harmful microorganisms. All PPE needs to be routinely cleaned.

Where Blood Borne Viruses are known / assumed to be present, extra controls should be used:

• Sharps containers: These are boxes that can safely hold needles. Do not use plastic sacks etc. Do not overfill boxes. This material is classed as clinical waste. The collection, storage and disposal of this waste is subject to strict controls.

• Equipment: Use the right equipment for picking up sharps; eg pincer tools, tongs, litter pickers dustpan and hand brush.

• Gloves: Always wear gloves when using tools to move needles. Gloves should give a high degree of puncture resistance. They do not provide adequate protection on their own, but give secondary protection in the case of accidental contact.

• Clothing: Where appropriate, also consider suitable puncture/ cut-resistant clothing to help protect limbs.

• First aid: Encourage the wound to bleed if the skin is punctured – do not suck the wound. Rinse thoroughly under running water. Wash out splashes to the eyes, nose and mouth with plenty of water – do not swallow the water. It is important to get prompt medical advice on any treatment needed.

Training requirements: Workers need to be aware of the microorganisms they may be exposed to and how to use the controls properly. They should also be made aware of the relevant signs / symptoms associated with any of these microorganisms and how to report these to managers.

External links for more information:

Mold Hazardous Substance Portal Page

UK Health and Safety Executive - Harmful Micro-organisms

UK Health and Safety Executive - Infection at Work

EPA - Flood Cleanup Fact Sheet

World Health Organization - Vector-Borne Diseases