How Air Pollution Affects Olive Oil Quality in California

Producers and researchers weigh in on the impact of wildfire smoke and air pollution on the local olive oil industry.
By Thomas Sechehaye
Oct. 11, 2023 13:30 UTC

The ongo­ing impact of cli­mate change has left much of the west­ern United States with air qual­ity prob­lems. According to a recent PBS report, the prob­lem is rooted in California’s San Joaquin Valley.

The south­ern half of California’s Central Valley is the heart of agri­cul­tural pro­duc­tion and dis­tri­b­u­tion. For the last 25 years, the region has been out of com­pli­ance with Environmental Protection Agency stan­dards.

See Also:California Olive Farmers Turn to Birds for Natural Pest Control

According to a report from KCRA, an NBC tele­vi­sion affil­i­ate in Sacramento, most Californians expe­ri­ence unhealthy lev­els of air pol­lu­tion. The 2023 State of the Air Report con­firmed that many California coun­ties receive fail­ing grades for smoke and ozone pol­lu­tion.

Air qual­ity improve­ments are under­way, such as trans­porta­tion ini­tia­tives, zero car­bon truck­ing, reduc­tion of agri­cul­tural burn­ing and find­ing ways to limit the risk of large wild­fires.

The good news is we’ve seen some improve­ments in a lot of places across the val­ley,” Congressman Josh Harder, who rep­re­sents com­mu­ni­ties in the San Joaquin Valley, told KCRA. The bad news is we still have a lot of work left to go.”

Harder empha­sized in the report that it is essen­tial to focus on pre­ven­tion, hire more fire­fight­ers and seek to pro­tect the health of future gen­er­a­tions by improv­ing air qual­ity – short and long-term.

Air pol­lu­tion is com­pounded in California by smoke from wild­fires. The California Department of Forestry and Fire Protection reported 5,474 wild­fires burn­ing 104,169 hectares in 2023.

Similar dam­age was reported in 2022. Contrast this with 2020, when more than 8,600 wild­fires con­sumed 1.7 mil­lion hectares and killed 33 peo­ple.

According to CalMatters, a non-profit news orga­ni­za­tion, California wild­fires emit as much car­bon as almost 2 mil­lion cars. In an increas­ingly vicious cycle, cli­mate change wors­ens fire, and fires worsen cli­mate change.

CalMatters reported that in 2020, the state’s wild­fires increased emis­sions by about 30 per­cent. Scientists from the University of California – Los Angeles describe the state’s efforts to achieve cli­mate goals as going up in smoke.”

According to a Baker Wine & Grape Analysis newslet­ter, there have been ques­tions in recent years about smoke taint in olives and olive oil. Thankfully, it seems as though olives fare much bet­ter than grapes in the pres­ence of wild­fire smoke,” the lab reported.

The newslet­ter cited Selina Wang, an asso­ciate pro­fes­sor at the University of California-Davis’ food sci­ence and tech­nol­ogy depart­ment, say­ing that olives are less sus­cep­ti­ble than wine­grapes to smoke taint thanks to thicker olive skins.

All crops, includ­ing olives, are vul­ner­a­ble to smoke taint, depend­ing on its matu­rity index and ripen­ing stage, the dis­tance between the orchard and active fire, how long the expo­sure to smoke con­tin­ued before har­vest, how close the fire to the har­vest period and rain event,” Wang told Olive Oil Times.

I am not aware of sig­nif­i­cant recent wild­fire effects on olive grow­ing and pro­duc­tion,” she added.

The pro­tec­tive cutic­u­lar wax, the fact that ash is insol­u­ble in oil, and the wash­ing step in the milling min­i­mize the oppor­tu­nity for smoke to taint olives and olive oil.

Most research on smoke taint has been done on wine grapes,” Wang said. Olives are thicker and have more waxy skins than grapes, so olives have nat­ural pro­tec­tions against smoke taint.”


From an air qual­ity stand­point, olive trees and olive farm­ing cre­ate far less air pol­lu­tion than farm­ing the annual crops that are replanted and tilled up every year to go into refined seed oils,” Samantha Dorsey, pres­i­dent of McEvoy Ranch, told Olive Oil Times. Because olive trees are per­ma­nent crops, they are sig­nif­i­cant car­bon sinks as well.”

Dorsey described McEvoy Ranch’s expe­ri­ence dur­ing times of poor air qual­ity.

With many years of wild­fire smoke pol­lu­tion in California, we have had lots of oppor­tu­nity to study our olives that have sat in smoke for weeks on end,” she said. We have found zero traces of smoke taint or the smoke taint marker, guia­col, in any of our olives or extra vir­gin olive oil.”

Olive oil is unique in that it does not absorb any of its aro­matic or fla­vor com­pounds until it is milled, which leaves the oil inside the olive on the tree quite pro­tected against wild­fire smoke,“ Dorsey added.

Looking at the big­ger pic­ture of envi­ron­men­tal impact, olive oil is supe­rior to other edi­ble oils.

From a long-term sus­tain­abil­ity stand­point (vis a vis air qual­ity and many other envi­ron­men­tal mark­ers), olive oil is supe­rior to any other edi­ble oil on the mar­ket,” Dorsey said.

Its pro­duc­tion inputs are com­par­a­tively low, the trees them­selves sequester car­bon at a fan­tas­tic rate, it is a per­ma­nent crop that does not require replant­ing each year (unlike seed oils), it is shelf sta­ble (unlike dairy), you can extract the oil phys­i­cally instead of chem­i­cally, and it is incred­i­bly healthy,” she added.


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