Issues with the catalytic converters of 862,520 Fiat-Chrysler vehicles are prompting a semi-voluntary recall, according to officials from the US Environmental Protection Agency (EPA) and the California Air Resources Board (CARB).

The vehicles in question include:

2011-2016 Model Year (MY) Dodge Journey

2011-2014 MY Chrysler 200/Dodge Avenger

2011-2012 MY Dodge Caliber

2011-2016 MY Jeep Compass/Patriot

The recall will be conducted in phases, with owners of older cars being notified first that they can bring their cars in to be fixed. The last phase is expected to begin in the fourth quarter of 2019. Unlike previous Fiat-Chrysler emissions recalls, these fixes require replacement parts.

The recall is voluntary in most states, but in California, compliance with the recall is mandatory. That means owners of the above Dodge-, Chrysler-, and Jeep-brand vehicles won't be able to register their cars in the Golden State without returning them for the necessary fixes.

In a press release, CARB noted that the Fiat-Chrysler vehicles in question emit excess nitrogen oxides, which "are the most important contributor to ambient ozone and a key contributor to fine particulate matter pollution (PM 2.5)." These two factors are "associated with premature death, asthma emergency room visits, increased hospitalizations due to exacerbation of chronic heart and lung diseases, and other serious health impacts."

In justifying its reasoning to make the recall mandatory, the board added that "California is home to both the highest ozone levels (South Coast) and ambient particulate matter levels (San Joaquin Valley) in the United States."

The EPA has begun doing more in-use vehicle testing since the Volkswagen Group diesel scandal that broke in 2015. Although the VW, Audi, and Porsche cars easily passed the automaker-administered laboratory tests, independent testing showed that the diesel vehicles emitted nitrogen oxide far in excess of the US legal limits while driving under real-world conditions.

In its press release today, the EPA said that each year it tests about 150 vehicles that are between one and four years old. For the most part, the agency still relies on manufacturer-provided laboratory tests.

Fiat-Chrysler's recall follows on another emissions issue that the company had with more than 100,000 diesel-powered trucks and SUVs. Those vehicles are required to receive a software update to bring them into compliance. In January, Fiat-Chrysler agreed to pay more than $300 million in a settlement related to the illegal pollution emitted by the non-compliant trucks and SUVs, as well as $185 million in "mitigation costs" related to the nitrogen oxides they emitted.