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The islands of Hawaii are known for their rugged volcanic landscapes and black sand beaches. However, the volcanoes that built these islands can also have negative impacts in the form of noxious gas emissions known as vog.

In short, vog refers to the hazy air pollution that results when sulfur dioxide and other gases emitted from Kilauea Volcano on Hawaii’s Big Island mix with moisture in the air. The result is a visible haze that impacts air quality and can cause health issues.

In this comprehensive guide, we will cover everything you need to know about vog in Hawaii, including what causes it, where it occurs, its environmental and health impacts, and how residents deal with this volcanic air pollution.

What Causes Vog in Hawaii

Kilauea Volcano Gas Emissions

The Kilauea volcano on Hawaii’s Big Island emits large amounts of sulfur dioxide gas during eruptions. This gas interacts with oxygen, sunlight, moisture and other gases in the atmosphere to produce the hazy mixture known as vog (volcanic smog).

Vog levels depend directly on the amount and type of volcanic activity occurring at Kilauea.

Chemistry Behind Vog Formation

When sulfur dioxide gas (SO2) is emitted from Kilauea, it reacts in the atmosphere to form tiny sulfuric acid droplets known as aerosols. Sunlight causes additional complex chemical reactions that convert the SO2 into other sulfur compounds like hydrogen sulfate and sulfate ions.

These reactions form very fine particles that scatter sunlight, causing the visible hazy conditions characteristic of vog.

Weather Patterns That Trap Vog

Vog can be blown downwind from Kilauea by trade winds and impact populated areas like Hilo and Kona for days at a time. Certain weather patterns like temperature inversions and low wind speeds tend to trap vog over parts of the island by preventing it from dispersing up into the atmosphere.

Vog concentration and movement depends heavily on daily wind flow around the Hawaiian islands.

Where Vog Occurs in Hawaii

Areas Downwind of Kilauea Crater

The volcanic smog, or vog, originates from the Halemaʻumaʻu crater at the Kilauea volcano’s summit on Hawaii’s Big Island. As the volcanic gases and ash erupt from the crater, they are carried downwind by the trade winds.

This means that areas located northeast through south of the crater typically experience the highest concentrations of vog.

Regions like Volcano village, Pahala, Ocean View, and Kau district on Hawaii’s Big Island see frequent vog clouds rolling in. Even the island’s largest city Kailua-Kona, about 30 miles northwest of the crater, gets smoky haze many days.

The vog is most dense closest to the crater and dissipates further away from the source.

Islands Impacted by Vog Transport

While the volcanic smog originates from Hawaii’s Big Island, the trade winds also transport it across the other islands in the Hawaiian chain. Islands to the southwest of the Big Island, like Maui, Molokai, Lanai, and even Oahu, experience vog when trade winds push the haze northwest.

Vog clouds have been recorded reaching as far as the western islands of Kauai and Niihau. However, the concentration is much lower the farther away the islands are. Nonetheless, vog can impact air quality and lead to health issues when inhaled across Hawaii.

Vog Monitoring in Hawaii

To track vog movement and concentrations in Hawaii, various monitoring networks have been set up:

  • Air quality stations across the islands measure sulfur dioxide and particulate levels.
  • Webcams show visibility at Hawaii Volcanoes National Park and schools or public areas.
  • Satellite data detects the density and movement of vog clouds using sulfur dioxide readings.

Real-time vog information allows health officials to issue guidance when air quality degrades to unhealthy levels. It also helps the public stay informed if vog conditions may worsen symptoms for sensitive groups.

Environmental Impacts of Vog

The volcanic smog or “vog” produced from Hawaii’s active volcanoes can have concerning environmental repercussions across the islands. From influencing native flora and fauna to contributing to climate change, understanding vog’s complex impacts is key.

Effects on Native Plants and Wildlife

Vog contains sulfur dioxide and other gases that can damage plants when absorbed through the leaves’ pores. Chronic vog exposure causes chlorosis and necrosis in native vegetation like hapu’u tree ferns and ohia trees.

This disruption of plants that support endemic birds and insects can reverberate up the food chain.

Researchers also found vog damages native birds’ feathers, impairing insulation and flight. Honeycreepers in high vog zones display stunted growth and constraints on reproduction. Intensified vog conditions could therefore endanger Hawaii’s unique forest bird communities over time.

Contribution to Ocean Acidification

According to the UH Manoa School of Ocean and Earth Science and Technology, vog emissions react chemically with atmosphere and seawater. As sulfur dioxide converts to sulfate particles and falls with rain or dust, it lowers ocean pH around Hawaii.

Analysis shows vog accounts for up to 24% of the excess CO2 absorbed by surface seawater. Resulting acidification near shore damages coral reef ecosystems and shellfish populations that Hawaiian fishing and tourism industries rely on.

Influence on Weather and Climate

Vog presence cools Hawaii’s near surface atmosphere but warms air at higher elevations. Scientists found Kīlauea volcano emissions helped form thermal inversions preventing vertical air mixing. Vog also affects cloud formation and solar radiation scattering to a degree that likely alters precipitation patterns.

On a broader scale, sulfate aerosols converted from SO2 gas reflect sunlight away from earth, producing a net cooling effect. But vog also contains substantial CO2 that traps heat. More research on ratio and transport of emissions influencing regional temperature and climate shifts would be valuable.

Health Effects of Vog Exposure

Respiratory Issues

Exposure to vog can cause irritation and inflammation in the lungs and airways. Common respiratory symptoms include coughing, wheezing, shortness of breath, chest tightness, and worsening of asthma symptoms.

Even healthy individuals may experience breathing difficulties when exposed to high levels of vog.

A study by the University of Hawaii found that emergency room visits for breathing problems increased by nearly 80% on Hawaii Island during heavy vog conditions from 2008-2013, compared to vog-free periods (Hawaii State Department of Health).

The elderly and those with pre-existing respiratory conditions are at greatest risk.

Impacts on Vulnerable Groups

Certain groups are especially vulnerable to the health impacts of vog, including:

  • Children – Their lungs are still developing, putting them at higher risk of respiratory issues.
  • The elderly – More likely to have pre-existing lung disease exacerbated by vog.
  • Those with asthma or other lung conditions – Vog can trigger asthma attacks and worsen chronic obstructive pulmonary disease (COPD).
  • Outdoor workers – Have greater exposure to vog through their jobs.

Pregnant women are also advised to take precautions, as some studies suggest vog exposure may be linked to adverse birth outcomes like preterm delivery.

Long-Term Health Consequences

The long-term impacts of prolonged vog exposure are still being investigated. However, chronic exposure may increase risks for certain cancers, heart disease, and DNA damage over time, according to preliminary studies.

One analysis estimated a 36% increase in heart disease mortality on Hawaii Island between 2008-2013 compared to 2000-2007, which may be linked to the island’s elevated sulfur dioxide levels from vog during that period.

Clearly, limiting vog exposure whenever possible is advised, especially for vulnerable groups. Using proper protective equipment like N95 masks can help mitigate risk. Staying informed on air quality reports is also key to reducing health impacts.

Living With Vog Pollution

Staying Informed on Air Quality

When vog events occur, it’s crucial to stay updated on real-time air quality conditions. The Hawaii Department of Health provides hourly Air Quality Index (AQI) ratings for locations across Hawaii through online maps and phone apps (see

These tools classify air quality ranging from “good” to “hazardous” based on particle pollution, sulfur dioxide, carbon monoxide and other indexes. Checking frequently allows residents to limit outdoor exposure when air conditions worsen.

Signing up for air quality text alerts is another smart tactic. The National Weather Service issues alerts when the AQI reaches “unhealthy” levels so individuals can take protective actions (

Staying plugged into air quality data resources is vital for reducing health risks during Hawaii’s unpredictable vog conditions.

Reducing Outdoor Activities During Vog Events

Since vog contains sulfuric acid and fine particles that irritate lungs, it’s wise to limit outdoor exertion when air quality declines. Instead of vigorous workouts, light indoor exercise is preferable.

Essential trips can be made using N95 masks, but extended driving or outdoor exposure is ill-advised.

Parents should also restrict children’s outdoor play when air conditions worsen. Schools and teams may cancel events, but individual youth activities should be minimized as well. Vog impacts growing lungs more severely, so keeping kids inside with fun distractions like movies or board games is sensible.

During major vog influxes, running air conditioners and closing windows can reduce indoor particulate levels. Although AC units don’t filter gases, limiting ventilation when outside air quality gets very poor may help marginally reduce irritation.

Staying aware of health advisories allows adjusting activities accordingly during Hawaii’s turbulent vog seasons.

Using Air Filters and Creating Clean Air Rooms

Specialized air purifiers with high-quality HEPA or activated carbon filters can effectively capture some vog particles and gases in home environments ( Units placed in frequently-used rooms can improve indoor air quality notably.

Filtered clean air shelters can also be created by closing doors and windows and running an air purifier continuously in a single room.

A low-cost alternative is using box fans with MERV 13 furnace filters taped to the backside. This DIY air filter can remove over 75% of fine particles when operated correctly (Source: IQAir). Strategically placing these fans to filter areas where family members spend most time can notably improve indoor air.

No filtration system fully eliminates all vog effects, however. So combining enhanced home air cleaning with conscientious steps like limiting exercise, wearing N95 masks outside, and heeding air quality warnings is essential for healthily navigating Hawaii’s volcanic haze.


As the eruptions of Kilauea continue, vog will likely remain part of life across parts of Hawaii. While frustrating, understanding what causes vog, how to monitor conditions, and how to protect health can help residents better deal with this volcanic air pollution.

Avoiding prolonged exposure and using common-sense precautions allows residents and visitors alike to still enjoy all that Hawaii has to offer despite persistent vog events.

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