When Kilauea sparked to life again in December, many in Hawaii were dreading the coming vog emissions that had dissipated after the volcano quieted in the fall of 2018 following 35 years of nearly continuous eruption.

They were not looking forward to the volcanic haze and smog that would cover the island chain when conditions were right, causing respiratory problems; headaches; eye, nasal and throat irritation; and more.

But following an initial strong burst of volcanic gases in the opening days of the Dec. 20 summit eruption at Halemaumau Crater, emissions backed off and have continued to diminish along with the volcano’s eruption rate.

“There’s almost no vog,” said Claire Horwell, director of the International Volcanic Health Hazard Network. “Emissions are very low.”

According to the U.S. Geological Survey’s Hawaiian Volcano Observatory, sulfur dioxide emissions were recently recorded at around 700 metric tons per day. That’s in contrast to the 40,000-plus metric tons per day in the first three days of the eruption.

Vog is the pollution formed from acidic gases and particles emitted from volcanoes. It is composed primarily of sulfur dioxide gas and its oxidation products, such as sulfate aerosol.

In Hawaii, depending on atmospheric conditions, the volcanic air pollution can spread far and wide, affecting people across the island chain.

When the tradewinds are working, usually only the areas southwest of Kilauea Volcano’s active vents experience vog as a visible haze or a sulfurous smell or taste. But when the trades are absent or the winds start blowing from the south, the entire state can be enveloped in the nasty mixture of sulfur dioxide and fine particulates.

People with asthma, lung and heart problems can be especially vulnerable, and so can older adults, infants and children, and pregnant women. Symptoms include coughing, runny noses, sore throats and headaches.

Tamar Elias, a scientist with the U.S. Geological Survey’s Hawaiian Volcano Observatory, said Kilauea is indeed emitting less sulfur dioxide and other gases than it was at the beginning of the eruption.

“This means that there is less vog being formed, since there is less gas,” she said.

At the onset of the new eruption, Kilauea summit emission rates reached 40,000 metric tons per day and higher, she said. But when the north fissure activity stopped on Dec. 26, sulfur dioxide emissions progressively dropped to around 2,500 tons per day by Jan. 11, a trend that continues today.

Elias said the amount of gas released by the volcano is proportional to how strong the eruption is, and the decrease in vog correlates to the volcano’s declining eruption rate.

“Not all eruptions are created equal,” Elias said. “Some are more effusive than others. This is an extremely well-behaved eruption.”

HVO scientists say lava activity is confined to Halemaumau, with lava erupting from a vent on the northwest side of the crater.

Varying emission rates are not unusual at Kilauea. They have gone up and down since the Hawaiian Volcano Observatory started routinely measuring them in 1979, when the summit was averaging about 500 metric tons a day.

Between 1983 and 2008, however, Kilauea’s Puu Oo eruption averaged around 2,000 metric tons a day. Following higher emission rates early in the summit eruption from 2008 to 2018, lava lake emissions stabilized near 5,000 tons a day, while Puu Oo emissions fell to a few hundred tons per day.

The destructive 2018 eruption — which pushed roughly 1 billion cubic yards of molten rock across the Lower Puna landscape, destroying 716 homes and forcing the evacuation of thousands of residents — recorded incredibly high emission rates of nearly 200,000 tons per day, the highest recorded emissions from Kilauea.

At the time, there were reports that Hawaii island medical providers were seeing an increase in patients reporting vog- related symptoms.

After the four-month eruption ended, total Kilauea emissions dropped to a measly 30 tons a day.

Horwell, a U.K. scientist who has studied ways to cope with vog, moderates a Facebook page called Vog Talk which was very active during the 2018 eruption. Many of the members of the page live on Hawaii island near the volcano.

The page was also quite popular during the opening days of the current event, but there haven’t been any new posts since Dec. 28.

“It’s quiet because there’s almost no vog,” Horwell said.