In a new report, the US Environmental Protection Agency (EPA) Air Enforcement Division (AED) estimates that the emissions controls have been removed from more than 550,000 diesel pickup trucks in the last decade.

The AED report includes only tampering that involves the complete removal and disablement of emissions controls hardware. This is known as a “full delete” of emissions controls. Other types of tampering are common, such as installing software tunes, but leaving emissions controls hardware intact and operational.

Number of full delete Class 2b and diesels by vehicle age Source: EPA.

As a result, more than 570,000 tons of excess oxides of nitrogen (NO_x) and 5,000 tons of particulate matter (PM) will be emitted by these tampered trucks over the lifetime of the vehicles.

Notably, the report does not provide an estimate of the prevalence of tampering; it quantifies the scale and air quality impact of the tampering of diesel pickup trucks that the agency has identified in recent civil enforcement efforts.

Specifically, AED analyzed evidence obtained by EPA civil enforcement personnel during many investigations conducted over approximately five years, involving tampering of Class 2b and 3 (GVWR 8,500 - 14,000 lbs) diesel pickup trucks that occurred after 2009 and before 2020.

Estimated number of Class 2b and 3 deleted diesels. Source: EPA

These tampered trucks constitute approximately 15% of the national population of diesel trucks that were originally certified with emissions controls. However, the report said, due to their severe excess NO_x emissions, these trucks have an air quality impact equivalent to adding more than 9 million additional (compliant, non-tampered) diesel pickup trucks to our roads.

The Clean Air Act prohibits tampering with emissions controls, as well as manufacturing, selling, and installing aftermarket parts that defeat those controls (aftermarket defeat devices). EPA has found numerous companies and individuals that have manufactured, sold, and installed both hardware and software specifically designed to defeat required emissions controls on motor vehicles.