Occurrence and Formation of Nitrosoamines in Drinking Water

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Occurrence and Formation of Nitrosoamines in
Drinking Water

• Richard Valentine
• Junghoon Choi
• Marcelo Mena
• Jason Assouline
• Zhou Chen

Department of Civil and Environmental
Engineering University of Iowa
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Discussion..

• What are they and why we should care.
• What we know about their formation from lab
  studies.
• Chemical plausibility.
• Summary of field assessment of NDMA occurrence in
  US and Canada.
• Ongoing source studies.

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Nitrosamine Structure
R1
N-Nitrosamines
O
N
N
R2
Secondary Amines
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The Concern

• Known to be formed in foods treated with nitrite
  or nitrate since 1960s.
• Used in manufacturing and found in products and
  associated wastes.
• Carcinogenic, teratogenic, and mutagenic in
  animals.
• Most broadly acting and most potent class of
  carcinogens.
• Possible absence of non-susceptible species.
• Direct alkylation of DNA by nitrosamines.

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Classical Nitrosation

• Chemical and biologically catalyzed mechanism.
• Acid/heat catalyzed.

2 H NO2- NHR1R2 ? ONNR1R2
nitrite precursor nitrosoamine
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Some History of NDMA in Drinking Water

• Found in Canadian drinking water in 1989.
• Maximum Allowable Concentration (MAC)set at 9
  ng/L in 1992 by the Ontario Ministry of the
  Environment.
• Formation from nitrosation of Thiram (herbacide)
  shown in 1995.
• EPA classifies NDMA as a probable human
  carcinogen in 1997.Sets 10-6 life time risk at
  0.7 ng/l.

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Some History of NDMA in Drinking Watercont

• Linked to rocket fuel contamination in 1998.
• CA action level for NDMA set at 20 ng/l, for a
  10-5 lifetime cancer risk in drinking water in
  1998.
• CA action level lowered to 10 ng/l in 1999.
• Observed in CA wells under influence of
  wastewater recharge in 2000 (water factories).
• Linked to water treatment in 2001.
• Water factories close in US (2002, 2003).
• A mechanism involving water chlorination proposed
  in 2002.

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Lab Studies Chlorine/Monochloramine Mediated
Formation of NDMA
HOCl NH3 ? NH2Cl H2O
ammonia
monochloramine
free chlorine

• (CH3)2 NH NH2Cl ? (CH3)2NNO
• DMA Monochloramine NDMA

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NDMA Formation by Monochloramine
Addition of 0.1mM DMA monochloramine _at_ pH 7
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NH2Cl Formation Pathway (Choi and Valentine,
2002 Mitch and Sedlak, 2002)
HOCl (CH3)2NH
(DMA)
NH3
k-2
k2
k_1
(CH3)2NCl NH3 (DMCA)
k1
k3
k-3
NH2Cl (CH3)2NH
k4
NH2Cl
H
(CH3)2NNH2 (UDMH)
(CH3)2NNO (NDMA)
k5
Other products (CH3)2NNNN(CH3)2
(CH3)2NNCH2
Figure 4. Monochloramine mediated NDMA formation
pathway
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Formation in DrinkingSource Water (River w/
Riverbank Filtration)
pH 8.2
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What is the nature of the precursor(s) ?
NDMA 7 Day Formation Potential (1 mM NH2Cl w/wo
DMA Additions)
Iowa River Water
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Formation of Other Nitrosamines by Reaction with
Monochloramine
Example
NH2Cl
nitrosodiphenylamine
diphenylamine
Nitrosodiproplyamine NDPA NitrosodiethylamineND
EA NitrosdibutylamineNDBA Nitrosomethylethylamine
NMEA NitrosomorpholineNMPL NitrospiperidineNPPD
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Formation of Other Nitrosamines by Reaction with
Monochloramine
0.1 mM precursor, 0.1 mM NH2Cl, pH 7.0
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NA Formation Related to pKa of Precursor
pH 7
Log NA/NDMA
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Formation of NAs in Chloraminated Wastewater
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AWWA/WEF Occurrence Study(Distribution System
Samples)
n 50 for samples with chloramine residuals n
29 for samples with free-chlorine residuals
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Coagulant Polymer DADMAC
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How is NDMA Formation Related to Source Water
Characteristics ?

• Organic nitrogen may not be a simple benign
  pollutant typically associated with nutrients as
  generally thought.
• Some drinking water sources are more susceptible.
• Are susceptible waters associated with
  agricultural related wastes and discharges ?

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Source Water Studies (UI/USGS)

• Collect samples (NAWQA)
• Measure NDMA Formation Potential
• -NDMA FP
• How ?
• 1 mM preformed monochloramine at pH 8.3 and 7.0
• 7 day incubation

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NDMA Formation Potential (January 2004 Sampling)
pH 7.0
pH 8.4
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Wapsipinicon River near Tripoli, IA
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Observations

• High but variable NDMA formation potential.
• Generally more formed at higher pH (may be due to
  stability of chloramines)
• Not yet clear if related to measurable
  differences in organic N

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Where are we now ?

• NDMA is definitely an issue. It is a new
  disinfection by-product. Just not sure how big
  of an issue yet.
• Complicated chemistry. Dont know nature of
  precursors or their sources very well.
• Other nitroso compounds may also form as DBPs but
  difficult to measure.
• Need for comprehensive risk assessments.

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........Some risks are the consequence of the
reduction in others. .The issue is frequently
one of choice Is it yours or someone elses..
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Risk Minimization