NDMA Formation during Chlorination and Chloramination of Aqueous Diuron Solutions

Abstract

Formation of the potent carcinogen N-nitrosodimethylamine (NDMA) during chlorine disinfection of water containing secondary amines is now generally acknowledged. The phenylurea herbicide diuron is one of the most widely used herbicides in California, has been frequently detected in California's water sources with a transient nature of appearance, and has a structure that suggests it might be an NDMA precursor. This study sought to quantify the potential for NDMA formation from aqueous diuron solutions under varied chlorine and chloramine conditions. NDMA formation was consistently observed even in the absence of added ammonia, which has usually been the source of the nitroso-nitrogen during chloramination of other precursors. It appears that both nitrogen atoms in NDMA are donated by diuron during chlorination in the absence of added ammonia. For a given chlorine and diuron dose, NDMA formation increased in the order OCl -<NH 2 Cl<NHCl 2 , a result consistent with previous NDMA formation studies. Significant quantities of NDMA (170 ng/L) were produced during dichloramination of diuron using a low dichloramine concentration and a diuron concentration at the upper end of typically detected concentrations in California (20 µg/L), suggesting a need for further investigation to accurately assess the human health risks posed by diuron with respect to NDMA formation potential. A reaction pathway is proposed to provide a possible explanation for NDMA formation from diuron during chlorination or chloramination. The findings in this study identify a specific potential precursor of NDMA formation, one that arises from non-point sources. This further highlights the difficulties associated with determining the environmental safety of chemicals and their associated byproducts.

Occurrence and profiling of multiple nitrosamines in source water and drinking water of China

“…Further, a recent study showed that NDMA may only account for~5% of the estimated total nitrosamines (Dai and Mitch, 2013). In general, these results suggested that disinfection by chlorine or chloramine and pre-oxidation during drinking water treatment could produce nitrosamines due to the presence of precursors, which is consistent with previous reports (Chen and Young, 2008;Kemper et al, 2010;W.J. Zhou et al, 2009;Q.…”

“…Among the 11 river water sources, the concentrations of the three nitrosamines in 6 source waters (DWTPs 4,17,18,35,51, and 54) were above 50 ng/L, which was probably correlated to the contamination of source water as indicated by high DOC (6.83, 4.28, 3.95, 4.36, and 3.16 mg/L for DWTPs 4, 17, 18, 35, and 54, respectively), ammonia (0.79, 0.47, and 0.45 mg/L for DWTPs 17, 18, and 54, respectively), and nitrate (10.9, 3.26, 3.01, 5.95, and 2.98 mg/L for DWTPs 4, 17, 18, 35, and 54, respectively) levels. In previous studies, relationship between nitrosamine-FP and these water quality parameters has been observed (Chen and Young, 2008;Choi and Valentine, 2003). In addition, DWTPs 4, 17, 18, 35, 51, and 54 were located in the middle and downstream of the river sources, so contamination contributions from the industrial and domestic discharge of nitrosamines could not be neglected (Mitch et The ratio of the sum concentrations of the nine nitrosamines in finished water to those in source water was 42.3% on the 75th percentile value basis (Supplementary Table D); the median and maximum concentrations of the nine nitrosamines in this study were 9.95 ng/L and 153.2 ng/L, respectively, which is similar to the US and Canada survey results.…”

“…The results in our survey indicated the presence of extensive discharge sources. Previous studies have shown that NDMA may be present in secondary effluents from sewage treatment systems and in effluents from industries including rubber, leather, pesticides, food processing, foundries and dyes (Chen and Young, 2008;Feng et al, 2009). NDEA, NDBA, NMor and NDPhA have been detected in emulsion products, such as condoms, baby bottle nipples, rubber, soothers and gloves, and in tobacco, meat and wines (Thilen and Shishoo, 2000;Verna et al, 1996).…”

The formation and control of emerging disinfection by-products of health concern

“…In addition, selected agricultural chemicals have been found to be NDMA precursors. For example, the phenylurea herbicide diuron reacts with chlorine or chloramines, especially dichloramine, to form NDMA (Chen & Young 2008). Recently, the fungicide tolylfluanide was found to undergo microbial degradation to N,N -dimethylsulphamide, which during ozonation had a high conversion rate to NDMA (Schmidt & Brauch 2008).…”

Analysis of the herbicide diuron, three diuron degradates, and six neonicotinoid insecticides in water-Method details and application to two Georgia streams

“…Additionally because some degradates are more stable than diuron, they can persist longer in the environment (table 1). Diuron can also be a disinfection by-product precursor; under certain water-treatment conditions, diuron can form N-nitrosodimethyl amine (NDMA) (Chen and Young, 2008), which is a class B2 carcinogen (reasonably considered to be a human carcinogen; U.S. Environmental Protection Agency 2010).…”