Environmental Odors

What it is

Many substances in the environment can produce odors. You typically smell these odors when you are outdoors and sometimes when you are indoors with your windows open.

You may smell and react to certain chemicals in the air before they are at harmful levels. Those odors can become a nuisance and bother people, causing temporary symptoms such as headache and nausea. Other chemicals can be toxic and cause harmful health effects.

Causes

Environmental odors can come from many sources:

• Animals: Confined animal feeding operations (CAFOs)
• Agriculture: Manure and chemical fertilizers or pesticides
• Human activities: Compost, sewage, garbage, fires, household cleaning agents
• Industry: Oil refineries, landfills, paper mills, wastewater treatment plants
• Nature: Moist soil, gardens, fires
• Vehicles: Diesel exhaust

Health impacts

Everyone reacts to odors differently. Some people are more sensitive to environmental odors than others. People who are more sensitive to an odor may have symptoms even at a low concentration of the odor in air. In general, as concentration levels increase, more people will have symptoms.

Risk for adverse health effects

Toxicity is the degree to which a substance (a toxin) can harm humans or animals. Toxicity depends on:

• The amount of a substance (concentration) in the air you breathe
• How often (frequency) you breathe that air
• How much time (duration) you spend breathing that air

More information on toxic substances can be found on ATSDR's Toxic Substances Portal.

Environmental odors are not toxic. However, if a substance level in air is high, happens often, and last a long time, the odor can become toxic. It also may cause adverse odor-induced health effects. If those conditions do not exist, odors are generally not toxic.

Who is at increased risk

If you are sensitive to environmental odors, you may react to low concentrations of a substance in air. The length of exposure is important whether you are sensitive or not. People with asthma, fetuses, children and older adults may be more sensitive to the effects of environmental odors.

The following groups may be more sensitive to environmental odors:

• Pregnant people
• People with asthma
• Children
• Older adults

Preventing exposure

People can reduce their exposure to environmental odors by:

• Staying indoors when environmental odors are strong
• Exercising indoors on bad odor days
• Leaving the area for a few hours
• Using your inhaler if you have asthma

Jogging and other forms of exercise increase your breathing rate, making you breathe in more of the odor. During bad odor days, exercising indoors or in another location can help.

Safety tools

The “What is that odor?” tool allows people to describe an odor and find the substance(s) that produce that odor. You can also look up a specific substance and find a description of its odor.

The EPA’s Toxic Release Inventory (TRI) allows users to search find chemicals released in your area.

Symptoms and first aid

Symptoms vary based on your sensitivity to the odor. Usually, symptoms will depend on the type of substance, its concentration in air, how often exposure occurs, how long exposure lasts. It may also depend on your age and your state of health.

Young children, the elderly, and pregnant people may be more sensitive to odors. In general, the most common symptoms are:

• Headaches
• Nasal congestion
• Eye, nose, and throat irritation
• Hoarseness, sore throat
• Cough
• Chest tightness
• Shortness of breath

These symptoms generally occur at the time of exposure. Their intensity depends on the concentration of the odor in air, how often you smell it, and how long exposure lasts.

Symptoms will pass when you move to an area where concentration of an odor in the air is below levels of irritation. Levels of irritation are the levels known to cause eye, nose, or throat irritation in people.

Symptoms may sometimes last when moving out of the exposure area. This happens when concentration of an odor is at or above levels of irritation and the exposure duration is longer.

What communities can do

The Agency for Toxic Substances and Disease Registry (ATSDR) develops public health consultations about hazardous waste sites or facilities. You can petition ATSDR to evaluate environmental health exposures in your community. However, ATSDR needs available environmental sampling data to conduct an evaluation. These data are typically gathered by the EPA or a state environmental regulatory agency.

Additionally, your community can:

• Keep personal odor diaries to track the odors in the community
• Organize to assess the effect environmental odors have on the community
• Find out whether there are local nuisance codes against odors and how they can report a violation
• Appeal to local government for policy changes
• Appeal to industry to make operational changes to reduce odors

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Odor diaries can help distinguish odor types and times of the day or night when odors are worse.

What's being done

The U.S. Environmental Protection Agency (EPA) regulates pollutants in outdoor air through the National Ambient Air Quality Standards (NAAQS). The NAAQS regulates:

• Carbon monoxide (CO)
• Lead (Pb)
• Nitrogen dioxide (NO₂)
• Ozone (O₃)
• Particulate Matter (PM)
• Sulfur dioxide (SO₂)

Sulfur dioxide is the only regulated air pollutant with a strong, pungent odor. Nitrogen dioxide also has a strong odor.

Under the Clean Air Act, EPA must control 187 hazardous air pollutants, also known as toxic air pollutants or air toxics. EPA controls those chemicals for their toxicity, not for their odor. EPA requires them to be controlled at the source that generates the emissions.

Although environmental odors are not nationally regulated in the United States, many cities and local governments have established nuisance odor regulations. You can find more information by contacting your city or county health department or your state environmental department.