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Course 850 - Health Hazards in Construction

Safety guides and audits to make your job as a safety professional easier

Biological Health Hazards

Pigeon droppings in an abandoned building

Biological agents include bacteria, viruses, fungi (mold), other microorganisms and their associated toxins. They have the ability to adversely affect human health in a variety of ways, ranging from relatively mild, allergic reactions to serious medical conditions, even death.

These organisms are widespread in the natural environment; they are found in air, water, soil, plants, and animals. Because many microbes reproduce rapidly and require minimal resources for survival, they are a potential danger in a wide variety of occupational settings.

Exposure to Biological Hazards


Exposure to biological hazards may occur during demolition, renovation, sewer work, work on air handling systems, or other construction work from contact with contaminated or disease-carrying materials, such as:

  • soil
  • water
  • insects (mosquitoes, ticks)
  • bird or bat droppings
  • animals
  • structures

In the construction industry, biological health hazards are most commonly found:

  • working in health care facilities
  • an accumulation of animal waste and the presence of rodents, insects and birds
  • during demolition and remodeling of old structures and buildings where there is likely the presence of mold
  • during clearing operations and the removal of plants, trees and other foliage
  • landscaping

Fungi (Mold) Hazards


Fungi (mold) are found everywhere–both indoors and outdoors, all year round. The terms fungi and mold are often used interchangeably, but mold is actually a type of fungi. There are many thousands of species of mold and most, if not all, of the mold found indoors comes from outdoor sources.

Mold seems likely to grow and become a problem only when there is water damage, high humidity, or dampness. Molds are organized into three groups according to human responses: Allergenic, Pathogenic and Toxigenic.

We will take a closer look at each of these types of molds in the next tab.

Allergenic Molds

Mold Explainer Video

Allergenic molds do not usually produce life-threatening health effects and are most likely to affect those who are already allergic or asthmatic. The human system responses to allergenic molds tend to be relatively mild, depending on individual sensitivities, typically producing scratchy throats, eye and nose irritations, and rashes.

Pathogenic Molds

Pathogenic molds usually produce some type of infection. They can cause serious health effects in persons with suppressed immune systems. Healthy people can usually resist infection by these organisms regardless of dose. In some cases, high exposure may cause hypersensitivity pneumonitis (an acute response to exposure to an organism).

Toxigenic Molds

Mycotoxins can cause serious health effects in almost anybody. These agents have toxic effects ranging from short-term irritation to immuno-suppression and possibly cancer. Therefore, when toxigenic molds are found, further evaluation is recommended.

Molds Affect on the Body

Molds produce and release millions of spores small enough to be airborne. They can also produce toxicagents known as mycotoxins. Spores and mycotoxins can have negative effects on human health. The most common route of entry into the body is through inhalation; mold has a characteristic smell–if you smell mold, you could be inhaling mold. Mold is generally visible; however, some of the most toxic mold spores are small enough to be considered respirable [less than 10 micrometers (10 μm) in diameter].

Ten Things You Should Know About Mold

  • Potential health effects and symptoms associated with mold exposures include allergic reactions, asthma, and other respiratory complaints.
  • There is no practical way to eliminate all molds and mold spores in the indoor environment; the way to control indoor mold growth is to control moisture.
  • If mold is a problem in your workplace, you must clean up the mold and eliminate sources of moisture.
  • Fix the source of the water problem or leak to prevent mold growth.
  • Reduce indoor humidity (to 30-60%) to decrease mold growth.
  • Clean and dry any damp or wet building materials and furnishings to prevent mold growth.
  • Clean mold off hard surfaces with water and detergent, and dry completely.
  • Absorbent materials, such as ceiling tiles, that are moldy may need to be replaced.
  • Prevent condensation on cold surfaces by adding insulation.
  • In areas where there is a perpetual moisture problem, do not install carpeting.

Remember, molds can be found almost anywhere; they can grow on virtually any substance, providing moisture is present.

Mold Cleanup

Approved Filtering Facepiece Respirator (Disposable)-any combination of N, R and P with efficiency 95, 99, or 100.
Half-Mask, Elastomeric, Air Purifying Respirator-any combination of N, R and P with efficiency 95, 99 or 100.

There are several things to be aware while cleaning up mold on a construction site. Here are a few things to remember.

  • Make sure the working area is well ventilated.
  • Place mold damaged materials in a plastic bag and discard.
  • Clean mold off hard surfaces and other non-porous materials with detergent and water. Make sure you dry it completely.
  • Disinfect these cleaned surfaces with one of the following household bleach solutions:
    • Use ¼ cup household bleach per 1 gallon of clean water for light contamination
    • Use 1 ½ cups household bleach per 1 gallon of clean water for heavy contamination.

Respiratory Protection for Exposures to Mold

Respiratory protection for exposure to mold will depend on the size of the particle and its level of toxicity. Whenever you smell or see the presence of mold, it is important to take precautions to limit your exposure to mold and mold spores. In order to limit your exposure to airborne mold, you need to wear, at a minimum, an N-95 respirator. If oil is present in the air, make sure to use either an R or a P designed filter.

Poisonous Plants

poisonous plants
Many native and exotic plants are poisonous to humans when ingested or if there is skin contact with plant chemicals. Poison sumac is just one example.

Many native and exotic plants are poisonous to humans when ingested or if there is skin contact with plant chemicals. However, the most common problems with poisonous plants arise from contact with the sap oil of several ever-present native plants that cause an allergic skin reaction—poison ivy, poison oak, and poison sumac.

Poison ivy, poison oak, and poison sumac release oil when the leaf or other plant parts are bruised, damaged, or burned. When the oil gets on the skin, an allergic reaction, referred to as contact dermatitis, occurs in most exposed people as an itchy red rash with bumps or blisters.

Plant Identification

You might have heard the old saying "Leaves of three, Let it be!" It is a helpful reminder for identifying poison ivy and oak, but not poison sumac which usually has clusters of 7-13 leaves. Even poison ivy and poison oak may have more than three leaves and their form may vary greatly depending upon the exact species encountered, the local environment, and the season.

Being able to identify local varieties of these poisonous plants throughout the seasons and differentiating them from common non-poisonous look-a-likes are the major keys to avoiding exposure.

Poison Ivy

poison ivy
Poison Ivy

If you are working in a wooded area, you want to be on the lookout for poison ivy. Here are a few things to remember about poison ivy.

  • Eastern poison ivy is typically a hairy, ropelike vine with three shiny green (or red in the fall) leaves budding from one small stem.
  • Western poison ivy is typically a low shrub with three leaves that do not form a climbing vine. May have yellow or green flowers and white to green-yellow or amber berries.

Poison Oak

Poison oak is usually a shrub with leaves of three, similar to poison ivy. Here are some other components of poison oak:

poison oak
Poison Oak
  • Pacific poison oak may be vine-like.
  • It may have yellow or green flowers and clusters of green-yellow or white berries.

Poisonous and Infectious Animals


Many different poisonous and infectious animals are found throughout the United States and workers should be aware of these health hazards before starting work in a specific location.


Rabies is a viral disease caused by infection of the central nervous systems of wild and domestic animals and humans. The initial symptoms of human rabies resemble those of other systemic viral infections, including fever, headache and disorders of the upper respiratory and gastrointestinal tracts. Recognizing that a person has been exposed to the virus and prompt treatment are essential for preventing rabies. Once clinical symptoms have begun, there is no treatment for rabies and almost all patients will die from the disease or its complications within a few weeks of onset.

Raccoons, skunks, foxes, and coyotes are the terrestrial animals most often infected with rabies in the United States. All bites by such wildlife must be considered a possible exposure to the rabies virus.

The most sensible way to avoid contact with rodents is to prevent rodents from infesting your work site. You must also follow safety precautions if you do come across a rodent infested area.

Safe Disposal

Safe disposal of rodents and proper cleaning and disinfection of rodent-inhabited areas are keys to minimizing exposure to the virus.

The Center for Disease Control specifically recommends following these steps for safe disposal and clean-up of dead rodents and/or rodent dropping:

  • Wear rubber gloves.
  • Thoroughly spray dead rodents, traps, droppings, and contaminated areas with a general household disinfectant.
  • Place disinfectant-soaked rodents into a plastic bag and seal it. Then place it into a second plastic bag and seal. If possible, burn or bury the bag or contact your local or state health department about other appropriate disposal methods.
  • Disinfect floors, countertops and other surfaces with a general household disinfectant.
  • Before removing the gloves, wash gloved hands in disinfectant, and then in soap and water. Thoroughly wash hands with soap and water after removing the gloves.
  • Disinfect all used traps, and then set them again or replace them.
  • Eliminate possible rodent nesting sites such as junk cars, old tires and trash piles. Do not leave animal food and water in feeding dishes overnight, and keep all food in rodent-proof containers.
  • Cut grass, brush and dense shrubbery within the immediate area of buildings.


Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. In the construction industry, where are biological hazards usually found?

2. Which type of molds do not usually produce life-threatening health effects?

3. When cleaning up mold at a construction site, what is the correct bleach solution for light contamination?

4. What are the indications that you may be exposed to poison ivy, poison oak, or poison sumac?

5. Once clinical symptoms have started, almost all patients will die from rabies within _____.

Have a great day!

Important! You will receive an "error" message unless all questions are answered.