If you employ workers and they work outdoors, it is your responsibility to protect them from outdoor hazards including:

  • ultraviolet radiation from the sun
  • heat stress
  • cold stress
  • adverse weather conditions
  • hazardous plants
  • Lyme disease and West Nile virus
  • wild animals and pests

What you’re required to do by law

Under the Occupational Health and Safety Act employers must:

  • take every precaution reasonable in the circumstances to protect workers, including protecting workers from outdoor hazards
  • supervise workers and give them information and instruction to protect their health and safety, including how to:
    • identify outdoor hazards
    •  prevent or minimize exposure
    • treat symptoms of exposure to the sun, hazardous plants, ticks or mosquitos
  • make sure:
    • supervisors know what is required to protect workers
    • appropriate personal protective clothing as required is provided, kept in good condition and used as required
  • make sure workers are aware of risks

Ultraviolet radiation from the sun

Hazard summary

Excessive exposure to the sun’s radiation over the years may cause premature skin aging, skin cancer, and cataracts.

People who work outdoors may experience damaging effects of ultraviolet (UV) radiation from the sun.

The UV levels are highest in spring and summer between 11 a.m. and 4 p.m. At noon on a clear summer day, for example, it can take only 15 minutes to cause a sunburn on unprotected fair skin.

Suggested precautions

If your workers may be working in direct sunlight when UV levels are high, they should:

  • limit the amount of time working outdoors in the sun from 11 am to 4 pm
  • seek shade as much as possible, especially during breaks
  • wear a wide brim hat (8 cm or more)
  • attach a back flap and visor to a construction helmet
  • wear tightly woven clothing covering as much of the body as is practical
  • wear eyeglasses that effectively filter ultraviolet rays
  • apply broad spectrum:
    • lip balm with a sun protection factor (SPF) of 30 or higher
    • sunscreen with an SPF of 30 or higher on exposed skin - reapply often if sweating heavily

Extreme temperatures and poor weather conditions

Heat stress

Working in extreme heat can put stress on the body’s cooling system.

Exposure to heat may lead to cramps, fainting, heat exhaustion and heat stroke when combined with other stresses such as hard physical work, loss of fluids and fatigue. Heat stroke can kill quickly.

For outdoor workers, direct sunlight is usually the main source of heat.

Learn more about heat stress and how to protect workers from heat related illness or injury.

Cold stress

Working in extreme cold may stress a worker’s heating system. Working in cold conditions may lead to cold-related illness, disability and death, when combined with other conditions such as hard physical work or fatigue.

Learn more about how to protect workers from cold stress from The National Institute for Occupational Safety and Health (NIOSH).

Hazardous plants

Throughout Ontario, there are hazardous plants that can cause painful reactions if they touch a worker’s skin. This includes:

Giant hogweed


Giant hogweed is scattered across southern and central Ontario.


Eye or skin contact with the giant hogweed sap can cause:

  • temporary or permanent blindness, severe blistering and burns on the skin
  • swelling, severe burns and painful blisters, usually within 48 hours, in combination with exposure to sunlight

The severity of skin reaction depends on individual sensitivity. For some people, effects can last for months and skin can remain sensitive to sunlight for years.

What it looks like

Giant hogweed has 2 distinguishing features:

  • its stalk has reddish purple blotches and speckles and coarse hairs
  • the leaves have unusual toothed edges like a jagged-looking maple leaf—in early May, leaves are about 30 centimeters in diameter

It is a large plant, growing up to 5 metres tall. Young plants form large rosettes up to 2 metres high with no flowers.

Mature plants send up flowering stems that produce large, white umbrella-shaped flower clusters up to 90 centimetres wide.

Wild parsnip


Wild parsnip, found throughout Ontario, is particularly common in eastern Ontario. It grows in abandoned yards, dumps, meadows, old fields, roadsides and railway embankments.


Reactions often appear as long spots or streaks on the skin and are commonly confused with the effects of poison ivy. This plant can cause effects the first time a worker touches it.

Exposure to sunlight, after handling the fruit, flowers or leaves of wild parsnip, can cause inflammation of the skin. Skin reactions may range from burning sensations and reddening of the skin to blistering and extreme burns.

What it looks like

In its first year, wild parsnip grows close to the ground in the form of rosettes with leaves averaging 6 inches long. Mature wild parsnip have flower stalks that grow to about 4 feet tall and umbrella-like clusters of yellow flowers that form large flat seeds.

Poison ivy


Poison ivy can be found throughout most of Ontario.

It grows in meadows, thickets in clearings, along the borders of woods, at roadsides, dumps and along fence lines.


Reactions may range from mild to severe itchy skin rashes.

There is oil throughout a poison ivy plant that may sensitize a worker’s immune system. This means the next time they touch it, the oil can cause an allergic skin reaction.

Tearing or bruising the plant can expose your skin to the oil. The oil can also:

  • spray from plants if you cut them
  • stick to clothing, boots and tools and transfer to other people by touching or rubbing

Smoke can carry the oil from a fire and a person exposed to the smoke may experience serious allergic respiratory or skin reactions.

What it looks like

Poison ivy has three leaflets. The stalk of the middle leaflet is longer than the stalks of the two side leaflets. Poison ivy can grow either:

  • as dwarf, shrubby plants carpeting the ground
  • as upright plants 60-90 centimetres high
  • in vine-like form around trees, shrubs and posts

Poison sumac

Where it grows

Poison sumac is a native shrub or small tree found in southern Ontario. You can find it in wet woods and at the edges of swamps and lakes.


The sap from poison sumac can cause an itchy rash for most workers. Both the foliage in summer and the bare branches in winter can cause a severe rash.

What it looks like

The plants have compound leaves with 3 to 6 pairs of leaflets that are nearly opposite each other, plus one terminal leaflet at the tip.

Pointed at the tip, leaflets usually have smooth edges and turn red in the fall. Flowers are dull white in hanging clusters. Berries are a whitish or drab colour.

Stinging nettle

Where it grows

Stinging nettle grows in large masses in old pastures, flood plains, woodland areas and along stream banks throughout Ontario.


Stinging nettle can cause a chemical dermatitis or skin inflammation from the acid in the hollow hair of the leaves and stems. When touched, the hairs penetrate the skin and break off, allowing the acid to enter the skin.

What it looks like

This plant grows up to one metre tall. Its leaves are dark green, egg-shaped, toothed and tapered. It measures 5 to 15 centimetres long and 2 to 5 centimetres wide. It is a flowering plant with hollow hairs on the leaves and stems, which contain acid and other chemicals.

Nettles flower from June to September and produce small hanging clusters of greenish-white flowers just above where the leaves attach to the stem.

Suggested precautions

During work

Workers who work outdoors should:

  • become familiar with hazardous plants in order to identify them by sight
  • never touch or brush up against any of these plants with bare skin
  • cover their body using impermeable coveralls and boots, rubber gloves, and use a face shield to protect their eyes and face from contact with a hazardous plant
  • avoid using power tools near or burning the plant—damage can release toxic sap or oil
  • wash all equipment  that has touched the plant, sap or oil

After work

Workers should:

  1. thoroughly wash their boots and rubber gloves first with soap, water and a scrub brush before taking off protective clothing
  2. remove clothing carefully to avoid contact with sap that may be on clothing
  3. wash rubber gloves before removing them
  4. remove protective eyewear if wearing them
  5. put non-disposable clothing in the laundry and wash with soap and water

What to do if a worker is exposed to hazardous plants

Workers should:

  1. wash the affected skin immediately with soap and cold water. It is important to use cold water because hot water opens the pores of the skin and increases the chances of the oil and sap being deeply absorbed
  2. stay out of sunlight and cover up exposed areas if they are exposed to giant hogweed or wild parsnip
  3. get medical attention immediately

Lyme disease

Lyme disease is an infection caused by bacteria called Borrelia burgdorferi.

In Ontario, only bites by blacklegged ticks (formerly called deer ticks) can spread the disease. Not all blacklegged ticks have the bacteria.

Learn more about what blacklegged ticks look like.


These ticks are more commonly found in woodlands, tall grasses and bushes and thrive in wet environments. It’s possible to encounter blacklegged ticks almost anywhere in Ontario because:

  • of climate change and warmer winter temperatures
  • they spread by travelling on migratory birds and deer

Lyme disease does not spread from person to person or by animals. However, animals may carry the infected ticks.

Outdoor workers are at risk of coming into contact with blacklegged ticks, especially those in southern Ontario who may work in wooded, bushy areas or in tall grasses.

Learn more about where blacklegged ticks live and find the latest information about Lyme disease risk areas on Public Health Ontario’s website.


Most symptoms of Lyme disease in humans usually appear between three and 30 days after a bite from an infected blacklegged tick.

Learn more about the signs and symptoms of lyme disease.

Workers should see their doctor or a healthcare provider right away, if they have symptoms, or are just feeling unwell in the weeks following a tick bite.

When seeing a doctor workers should tell them about their outdoor occupation, and if they have been working in an area where they may have had exposure to ticks. Antibiotics can successfully treat most cases of Lyme disease.

Suggested precautions

During work

Workers should wear:

  • light-coloured clothing to help find ticks more easily
  • long sleeve shirts and long pants
  • a hat if contact with overhead vegetation cannot be avoided
  • closed footwear and socks

Workers should also:

  • tuck their pants into their socks
  • use an insect repellent, or bug spray, containing DEET or icaridin on clothes and exposed skin (always read the label for directions on use)
  • avoid bushy areas and long grass if possible

After work

Workers should:

  • do a total body inspection for ticks immediately
  • pay close attention to areas such as the scalp, ankles, armpits, groin, naval and behind the ears and knees
  • use a mirror to check the back of the body or have someone else check for them
  • shower soon to wash off a tick that may not be attached through a bite
  • check any equipment or gear for ticks before bringing it inside
  • put clothes in the dryer for one hour on high heat to kill any ticks

If workers find any ticks, they should report it to you so that other workers can be made aware of the hazard and recheck themselves for ticks.

Treatment and removal of ticks

Removing attached ticks within 24 hours can decrease the risk of infection.

Learn how to remove a tick safely and how Lyme disease is diagnosed and treated.

Report workers with Lyme disease

If you become aware that a worker has developed Lyme disease from exposure at work, it is your responsibility to report this to the Ministry of Labour as an occupational illness.

Mosquitoes and the West Nile virus

Some mosquitoes carry and can infect humans with the West Nile virus.

The chance of an infected mosquito biting and infecting a person is very small, but, as a safety precaution, it is important you take measures to minimize exposure of your workers to mosquitoes. This is especially important in areas where West Nile virus activity has been documented.

Visit the Ministry of Health and Long Term Care to learn more about protective measures against the West Nile Virus.

Wild animals and pests

Workers may encounter many pests outdoors, depending on the location. These include:

  • ants
  • stinging flying insects (bees, wasps, and hornets)
  • chiggers
  • arachnids (various spiders)
  • native snakes
  • exotic marine life
  • rodents
  • biting insects like flies and mosquitoes

When working in an area where they may encounter these pests, appropriate clothing should be worn, for example long pants, shirts in light colours. Workers should avoid wearing heavy perfumes or aftershave and apply repellents directly to clothing.

Learn more about protecting workers from: