A study carried out by a team of researchers at the School of Life Sciences, Puducherry University, in 2002 found that rats when administered graded doses of 10-100 micrograms of NPEO per kg showed significant decreases in sperm counts over three weeks. The study demonstrated that the graded dosage depleted antioxidant defence systems in sperms as well as loss of weight in testes and epididymides.

A study by researchers of IIT Roorkee revealed that wastewater treated at the Kondli sewage treatment plant in Delhi had high NP content. This water reaches the river Yamuna. The study was published in the September 5, 2007 issue of the journal, Toxicology and Applied Pharmacology.

A 2003 study at Royal Holloway, University of London found that oyster larvae exposed to 0.1 ppb of NP developed sexual deformities.

In 2005, University of Texas researchers showed that NP exposure increased cancer incidence in mice.