Daimler on Sunday condemned the studies, done by the same research body which sponsored another experiment forcing monkeys to inhale toxic exhaust fumes from a polluting diesel Volkswagen equipped with illegal software.
The study reportedly compared exhaust fumes and particulates with a then-new diesel-powered VW Beetle with those of an old Ford ute.
The controversy over Volkswagen AG's diesel-emissions cheating took another twist when the carmaker apologized for a test that exposed monkeys to engine fumes to study effects of the exhaust. In 2015, the US Environmental Protection Agency (EPA) published findings that Volkswagen had programmed software in its diesel cars so that they would pass emissions tests despite not meeting environmental regulations. In an official statement, the automaker has apologised for "the lack of judgement of individuals" involved in ordering the tests, and admits that "the scientific methods chosen then were wrong". "And it comes on the tail of the emissions scandal, which was ethically problematic in the first place".
While two of the three auto makers have distanced themselves from the study, the results of which have never been published, Volkswagen has apologised for its part in the test.
The New York Times said VW and other German auto makers used the European Research Group on Environment and Health in the Transport Sector, known as EUGT, to conduct the research.More news: First lady visits Holocaust museum
The European Research Group on Environment and Health in the Transport Sector (EUGT) commissioned the study, the paper said.
"We are conscious of our social and corporate responsibilities and are taking the criticism regarding the study very seriously", said a Volkswagen Group statement on Monday to a variety of news organizations. Reports of the tests followed a New York Times account of similar experiments on monkeys in the U.S., triggering political recriminations and prompting automakers to distance themselves from the work.
These tests, conducted by Aachen University in Germany in 2013 and 2014, and also commissioned by the EUGT, saw 25 young healthy adults inhale varying concentrations of nitrogen dioxide for several hours each. The objective of one of the studies was to determine the health effects of diesel exhaust fumes in the workplace, such as those of mechanics and welders. It sees a parallel to "fake science methods" in other industries in which scientists were paid "to trivialize the health damage of their products and avert harsher laws". "We believe the animal tests in this study were unnecessary and repulsive".
"The minister has no understanding for such tests, which damage animals and humans and that do not serve science but merely PR aims", Mr Strater said.
The Care 2 Petition Team has launched a petition to urge Volkswagen to take responsibility for their actions by pledging to never again use animals for their research and to donate a satisfactory amount of money to a rescue organization that rescues animals from experimentation.
One member of VW staff involved in the study was said to be James Liang, the company's head of diesel competence in the US.