&EPA
United States
Environmental Protection
Agency
Office, of Research and
Development
Washington DC 20460
EPA/600/R-98/067
June 1998
Environmental Profile for
N-Methylpyrrolidone
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EPA/600/R-98/067
June 1998
ENVIRONMENTAL PROFILE FOR N-METHYLPYRROLIDONE
By
Research Triangle Institute
Research Triangle Park, NC 27709-2194
and
Science Applications International Corporation
Reston, VA20190
Contract No. 68-C6-0027
Project Officer:
Kenneth R. Stone
Sustainable Technology Division
National Risk Management Research Laboratory
Cincinnati, OH 45268
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
Printed on Recycled Paper
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Notice
The information contained in this document has been funded wholly or in part by the U.S.
Environmental Protection Agency under Contract 68-C6-0027 to Science Applications
International Corporation and through a subcontract from Science Applications International
Corporation to Research Triangle Institute. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
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Foreword
The U. S. Environmental Protection Agency is charged by Congress with protecting the
Nation's land, air, and water resources. Under a mandate of national environmental laws, the
Agency strives to formulate and implement actions leading to a compatible balance between
human activities and the ability of natural systems to support and nurture life. To meet this
mandate, EPA's research program is providing data and technical support for solving
environmental problems today and building a science knowledge base necessary to manage our
ecological resources wisely, understand how pollutants affect our health, and prevent or reduce
environmental risks in the future.
The National Risk Management Research Laboratory is the Agency's center for
investigation of technological and management approaches for reducing risks from threats to
human health and the environment. The focus of the Laboratory's research program is on
methods for the prevention and control of pollution to the air, land, water and subsurface
resources; protection of water quality in public water systems; remediation of contaminated sites
and groundwater; and prevention and control of indoor air pollution. The goal of this research
effort is to catalyze development and implementation of innovative, cost-effective environmental
technologies; develop scientific and engineering information needed by EPA to support regulatory
and policy decisions; and provide technical support and information transfer to ensure effective
implementation of environmental regulations and strategies.
This publication is a product of the Laboratory's Life Cycle Engineering and Design
research program, an effort to develop life cycle assessment and evaluation tools that can be
applied for improved decision-making by individuals in both the public and private sectors. Life
Cycle Assessment is a part of the Laboratory's strategic long-term research plan. This document
is published and made available by EPA's Office of Research and Development to assist the user
community and to link researchers with their clients.
E. Timothy Oppelt, Director
National Risk Management Research Laboratory
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Abstract
This project is sponsored by the U.S. Department of Defense's (DoD's) Strategic
Environmental Research and Development Program (SERDP) and led by the U.S. Environmental
Protection Agency's (EPA's) Life Cycle Assessment (LCA) Research Team at the National Risk
Management Research Laboratory (NRMRL). The research effort described in this report was
conducted to support the Life Cycle Engineering and Design (LCED) Program, a cooperative
program of both DoD and EPA. Among the objectives of the LCED is demonstrating the
effectiveness of analytical tools and environmental techniques to reduce impacts to the
environment and costs of operation while maintaining performance standards. The lessons
learned from LCED projects will be incorporated into a design guide for DoD process engineers
and designers. Environmental information on N-methylpyrrolidone (NMP) is required for the
development of the design guide. This report presents information related to the potential
environmental implications of NMP.
IV
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Table of Contents
Section
Page
1.0 Introduction 1-1
1.1 Goals and Scope of this Research 1-1
1.2 Research Approach 1-2
1.3 Report Organization 1-2
2.0 Production and Use of NMP 2-1
2.1 Production 2-1
2.2 Use 2-2
3.0 Impact Categories 3-1
3.1 Ecological Impacts 3-1
3.2 Human Health Impacts 3-1
4.0 Data Review 4-1
4.1 Sources 4-1
4.1.1 Literature Search - 4-1
4.1.2 Internet Search 4-5
4.2 Physical and Chemical Properties 4-9
4.3 Environmental Fate and Transport 4-10
4.4 Toxicity 4-12
4.4.1 Human Data 4-12
4.4.2 Laboratory Animal Data 4-14
4.4.3 Toxicokinetics 4-18
5.0 Impact Assessment 5-1
5.1 Human Populations at Risk 5-1
5.2 Natural Resources/Ecosystems . 5-4
5.2.1 Aquatic Toxicity 5-4
5.2.2 DataNeeds 5-5
6.0 Environmental Regulations 6-1
7.0 Summary .7-1
8.0 References 8-1
Appendix A N-Methylpyrrolidone Case Studies A-l
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List of Tables
Table
Page
3-1 Ecological Impact Categories Related to Chemical and Nonchemical Stressors
and Resource Depletion 3-2
3-2 Human Health Impact Categories Related to Chemical and Nonchemical
Stressors 3-2
4-1 Literature Search for NMP and PC 4-1
4-2 Specific Topic Literature SearchforNMP andPC 4-2
4-3 Internet Searches for NMP Environmental Profile Data 4-5
4-4 NMP Physical and Chemical Properties 4-9
4-5 NMP Biodegradability Test Results 4-11
5-1 Results of NMP Aquatic Toxicity Testing 5-4
6-1 Regulatory Information for NMP 6-1
VI
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Acronyms
BCF Bioconcentration factor
BOD Biological oxygen demand
CAA Clean Air Act
CARC Chemical agent-resistant coating
CAS Chemical Abstract Service
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
COD Chemical oxygen demand
cP Centipoise
DoD U.S. Department of Defense
EC Effective concentration
EPA U.S. Environmental Protection Agency
EPCRA Emergency Planning and Community Right-to-Know Act
HAP Hazardous air pollutant
LCA Life cycle assessment
LCED Life Cycle Engineering and Design Program
LD50 Lethal dose to 50 percent of test animals
MEK Methyl ethyl ketone
MSDS Material safety data sheet
NFPA National Fire Protection Association
NMP N-methylpyrrolidone
Pa Pascals
PC Propylene carbonate
ppm Parts per million
POTW Publicly owned treatment works
PVA Polyvinyl acetate
PVC Polyvinyl chloride
RCRA Resource Conservation and Recovery Act
SARA Superfund Amendments and Reauthorization Act
SERDP Strategic Environmental Research and Development Program
TLV Threshold limit value
TOC Total organic carbon
TSCA Toxic Substances Control Act
VOC Volatile organic compound
ฐC Degrees Celsius
ฐF Degrees Fahrenheit
vn
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1.0 Introduction
The research effort described in this report was conducted under cooperating programs of
both the Department of Defense (DoD) and the Environmental Protection Agency (EPA).
Among the shared objectives of the cooperators is demonstrating the effectiveness of analytical
tools and environmental techniques to reduce environmental impacts and costs of operation while
maintaining performance standards. This project was sponsored by DoD's Strategic
Environmental Research and Development Program (SERDP) and conducted by EPA's Life
Cycle Assessment Research Team at the National Risk Management Research Laboratory
(NRMRL).
STRATEGIC ENVIRONMENTAL RESEARCH AND DEVELOPMENT PROGRAM
SERDP
Strategic Environmental Research
and Development Program
Improving Mission Readiness Through
Environmental Research
addition, it is expected that many techniques
public and private sectors.
SERDP was established 2 years ago in order to
sponsor cooperative research, development, and
demonstration activities for environmental risk
reduction. Funded with DoD resources, SERDP is
an interagency initiative between DoD, the
Department of Energy (DOE), and EPA. SERDP
seeks to develop environmental solutions that
improve mission readiness for federal activities. In
that are developed will have applications across the
LIFE CYCLE ASSESSMENT RESEARCH PROGRAM
Since 1990, the NRMRL has been at the forefront in the development of life cycle assessment
(LCA) as a methodology for environmental assessment. In 1994, NRMRL established an LCA
Team to organize individual efforts into a comprehensive research program. The LCA Team
coordinates work in both the public and private sectors with cooperators ranging from members
of industry and academia to federal facility operators and commands. The team has published
project reports and guidance manuals, including Life Cycle Assessment: Inventory Guidelines
and Principles and Life Cycle Design Guidance Manual. The work described in this report is a
part of an expanding program of research in LCA taking place under the direction of NRMRL in
Cincinnati, OH.
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The research effort described in this report was conducted under the Life Cycle
Engineering and Design (LCED) program, a cooperative program of both the DoD and EPA.
Among the objectives of the LCED program is demonstrating the effectiveness of analytical tools
and environmental techniques to reduce impacts to the environment and costs of operation while
maintaining performance standards. To do this, LCED has sponsored three LCA and life cycle-
based projects at DoD installations:
Propylene Carbonate (PC) Blend 2, a depainting alternative to methyl ethyl ketone (MEK)
Chemical agent-resistant coating (CARC)
GBU-24 energetics model.
The lessons learned from these three projects will be incorporated into a design guide for
DoD process engineers and designers. Environmental information on N-methylpyrrolidone
(NMP) is required for the development of the design guide. This report presents information
related to the potential environmental implications of NMP.
1.1 Goals and Scope of this Research
The overall goal of this research is to document the environmental impacts of NMP to
assist DoD in assessing the life cycle environmental implications of NMP and NMP-based
formulations as viable alternative materials, products, and techniques to paint, depaint, and
corrosion control DoD aircraft, vehicles, and equipment in common applications at federal
facilities.
A life cycle study encompasses the cradle-to-grave stages of a product, process, or
activity, from the acquisition of raw materials to the final disposition. Consistent with life cycle
concepts, the study boundaries for the use of NMP in painting and depainting operations include
the following elements:
Raw materials acquisition
Production of intermediate chemicals and materials
Production of NMP
Use of NMP
Storage and disposal of residual NMP.
Although all stages of the NMP life cycle were considered, greater emphasis was placed
on the use, storage, and disposal stages because these are the stages over which DoD facilities
can exert the most control.
1.2 Research Approach
Identifying the life cycle environmental implications of NMP in DoD painting and
depainting operations requires not only a comprehensive search for the use of NMP in those
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operations but also a search for information related to the production, use (in other applications),
and disposal of NMP.
To develop an environmental profile for NMP, the following tasks were conducted and
documented:
Conducted a literature search of NMP for all environmental impact information and
data that can be reasonably acquired
Collected analyses of the environmental impacts of NMP as used in painting and
depainting operations
Contacted responsible individuals in the aerospace industry who have evaluated NMP
and NMP substitutes, as well as those currently using NMP
Provided detailed information on the known ecological and human health impacts of
NMP, including occupational health and safety implications of the use of NMP in
aerospace cleaning and depainting operations
Collected relevant case histories on the use of NMP for cleaning and depainting
operations.
1.3 Report Organization
This report is organized according to the following sections:
2.0 Production and Use of NMP
3.0 Impact Categories
4.0 Data Review
5.0 Impact Assessment
6.0 Environmental Regulations
7.0 Summary
8.0 References.
Section 2.0 provides background information on NMP and presents several case studies
focusing on its use in depainting operations. Key human health and environmental impact
categories are identified in Section 3.0. Section 4.0 discusses sources of information, physical
and chemical properties, environmental fate and transport, and the toxicology of NMP. Section
5.0 identifies the populations at risk of exposure and summarizes the available data on potential
impacts to natural resources and ecosystems. Current environmental regulations are reviewed in
Section 6.0, and a summary is provided in Section 7.0.
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2.0 Production and Use of NMP
The process used to manufacture NMP is summarized below. The relatively low vapor
pressure and high flash point of NMP, as compared to other solvents, make it suitable for use in
painting and depainting operations. However, there has been some concern about the potential
environmental and human health impacts associated with the use of NMP. In particular, focus
has been placed on the human reproductive impacts of NMP.
A life cycle evaluation of NMP requires an assessment of all potential impacts associated
with its production and use. Section 2.1 summarizes the steps involved in the manufacture of
NMP, starting with the extraction and processing of natural gas to the manufacture of the final
NMP product. Section 2.2 contains summaries of case histories regarding the use of NMP in
paint and depainting operations, as well as other applications that provide similar exposure
scenarios.
2.1 Production
A flow diagram and description of the process required to manufacture NMP are'
presented in Life Cycle Assessment for the PC Blend 2 Aircraft Radome Depainter (U.S. EPA,
1996a). N-methylpyrrolidone is manufactured by combining y-butyrolactone with methylamine.
Production of methylamine begins with the production and processing of natural gas. Natural
gas and steam are fed into a reformer over a nickel catalyst, where 70 percent of the feed is
converted into hydrogen and carbon dioxide. The remaining hydrocarbons are fed into a second
reformer, where air is introduced to supply nitrogen. The nitrogen and hydrogen react to form
ammonia. Methanol, which is manufactured from methane-rich natural gas, is used to alkalize
the ammonia in the presence of a dehydrating catalyst to produce methylamine.
The y-butyrolactone used in NMP production is produced from the combination of
acetylene and formaldehyde. First, acetylene and formaldehyde are reacted at 90 to 100 ฐC and
an acetylene partial pressure of 500 to 600 kPa. 1,4-Butynediol, which is produced from the
reaction, is then hydrogenated to 1,4-butanediol through the Reppe process. The y-butyrolactone
is then manufactured by dehydrogenation of 1,4-butanediol.
NMP production is accomplished by condensing y-butyrolactone with methylamine at
200 to 350 ฐC and 10 MPa. The total energy required to produce 1,000 pounds of NMP from
raw material acquisition through NMP production equal 28,526,000 Btu for material resources,
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16,934,000 Btu for process energy, and 918,000 Btu for transportation. A flow diagram of this
process is shown on page A-4 of Life Cycle Assessment for the PC Blend 2 Aircraft Radome
Depainter (U.S. EPA, 1996a).
N-methylpyrrolidone is primarily manufactured in the United States by three chemical
companies:
BASF, Inc.
ARCO Chemical Company
International Specialty Products (ISP) Technologies Inc.
U.S. Patent Nos. 5,049,300, 5,049,314, 5,478,491, and 5,575,859 contain information about
various paint strippers that use NMP in their composition.
2.2 Use
The low volatility and high flash point of NMP make it suitable for use in painting and
depainting and other industrial stripping and cleaning operations. This sections contains
summaries of case studies conducted using NMP in painting and depainting operations, as well
as in other applications that entailed similar exposure scenarios to the painting and depainting
operations. The case studies are summarized here to highlight applications and situations where
the performance of NMP has been evaluated and documented.
More extensive case study summaries are provided in Appendix A.
Pollution Prevention Demonstration and Evaluation of Paint Application Equipment and
Alternatives to Methylene Chloride and Methyl Ethyl Ketone (JM. Elion et al, EPA/600/SR-
96/117, October 1996).
This research provides results of a demonstration of NMP as a possible alternative to
methylene chloride and MEK. The demonstration was conducted at the Marine Corps Logistics
Base in Albany, GA. N-methylpyrrolidone was chosen because it effectively removed CARCs in
laboratory tests, is nonflammable, and is not classified as a hazardous air pollutant (HAP) by
EPA. However, NMP had to be heated to be effective in the demonstration. If employed, this
substitution would potentially reduce HAPs at the base by 11 percent from 1992 levels.
Surface Tension Modification of NMP-based Paint Strippers (W.C. Walsh, BASF
Corporation, Chemicals Division, Mount Olive, NJ).
Five NMP-based formulas, ranging in weight percent content from 12 to 80 percent, were
reviewed in this study to determine their effectiveness as paint strippers. All of these
formulations demonstrated good paint-stripping ability in the removal of commonly used paints
and coatings. During testing, performance data were developed on the ability of these products
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to strip acrylic latex, alkyd, polyurethane, and epoxy coatings from wood substrates.
Characteristics evaluated in this study included work area solvent concentrations, material
recyclability, waste generation, waste disposal, and stripping cost. In addition, by lowering the
surface tension of these NMP formulas, the time required for their use may be decreased by as
much as 40 percent. Even after reducing the time required to strip urethane enamel and
household epoxy, the NMP formulas were slower than the methylene chloride product.
N-methylpyrrolidone works slower but provides the user a working environment containing less
solvent vapor.
Initial Screening of Chemical Ingredients and Substitutes in Consumer and Small Shop Paint
Stripper Formulations (Sherry Wise, Regulatory Impacts Branch, Economics, Exposure and
Technology Division, Office of Pollution Prevention and Toxics, U.S. Environmental
Protection Agency, Washington, D.C., June, 1994).
This report contains information on chemical ingredients of commercially available paint
stripper products used to remove paint and other finishes by consumer do-it-yourselfers or small
shop operators (e.g., furniture restorers and refinishers). Coatings in the evaluations included
alkyd enamels, latex semigloss enamels, flat acrylic latexes, spar varnishes, urethane varnishes,
latex exterior enamels, interior vinyl acrylics, epoxies, marine paint, and marine varnish. Eight
NMP-based strippers were rated below methylene chloride-based products on all coatings but
above ATM strippers (mixtures of acetone and/or toluene and/or methanol), with the exception
of enamel, where both NMP and ATM were rated equally. N-methylpyrrolidone was the fastest
of the "safe" products (15 minutes to more than 1 hour, depending on the concentration of NMP).
Each NMP-based product also had a slight odor and was nonflammable. However, they cost
nearly twice as much as methylene chloride removers. They can also cause dizziness and nausea
after prolonged exposure.
Replacement of MEK with N-Methylpyrrolidone (NMP) in Coatings Plant Resin Clean Up
Operations (W.C. Walsh, BASF Corporation, Chemicals Division, Mount Olive, NJ).
This research discusses work conducted by a manufacturer of high-solids, oven-cured,
clear-coat, and base-coat coatings for Original Equipment Manufacturer (OEM) automotive and
heavy equipment, as well as for some industrial applications, to evaluate replacing its MEK
cleaning solvent with NMP systemwide. Results from the study showed that over a 10-month
test period there was a 5-fold decrease in MEK emissions from the facility and that cleaning costs
rose by 40 percent over total MEK costs. But, this result was due to the inexperience of the
facility in initially using NMP. The total volume of cleaning solvent passing through the plant
decreased by 39 percent, 69 percent of which could be accounted for by decreases in virgin MEK
purchases. Also, the total volume of MEK passing through the plant decreased by almost 72
percent.
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Met-Ed/Penelec Business and Industry, Technology Excellence Center (BITEC), BITEC
Assistance Report for James River Corporation, Lehigh Valley, PA (Concurrent Technologies
Corporation, 1450 Scalp Avenue, Johnstown, PA, May 1996).
James River Corporation manufactures both wax-coated paper and plastic (high-impact
polystyrene polymer) drinking cups at its Lehigh Valley, PA, facility. The plastic cups are
manufactured using aluminum thermoforming tools, with up to 100 vent holes in each tool.
These tools were removed and placed in an immersion tank filled with Tower 19 paint thinner, a
mixture of 80 percent toluene and 20 percent acetone, for 15 to 30 minutes and then allowed to
air-dry. Once dry, the vent holes were manually probed to remove the accumulated polystyrene
using a drill bit.
Based on a visual examination, NMP was the most effective of the three cleaners tested,
removing residues from recessed areas and small holes. N-methylpyrrolidone also did not emit
obvious odors during testing. Drying times were relatively high - some parts were still wet after
drying for 20 to 25 minutes at ambient temperature. At the time, NMP was available for
approximately $2.35/lb or approximately $1,000 to $l,150/55-gal drum.
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3.0 Impact Categories
A life cycle evaluation of the potential impacts of NMP requires consideration of impacts
both to the environment and to human health. To assist in guiding the search for information
related to NMP, impact categories and subcategories were established. Numerous impact
categories have been proposed for life cycle impact assessment, and most LCAs to date have
selected from these previous efforts in lieu of defining their own impact categories. However,
impact categories are typically selected so that the goals of the study may be satisfied.
This section lists the categories and subcategories of impacts to the environment and to
human health that were selected as starting points for the evaluation of NMP. For each category
and subcategory, quantitative and qualitative impact information was searched for and compiled,
as appropriate. Any additional impacts found that were not part of the original listing were
subsequently added.
3.1 Ecological Impacts
Potential ecological impacts of NMP as used in painting and depainting operations result
primarily from the production, use, and disposal stages of its life cycle, where emissions are
released directly into the environment. Examples of activities that might result in environmental
impacts could include the extraction and processing of natural gas, the volatilization of NMP
during use, or the leaching of residual NMP into the soil or ground water. To establish a baseline
set of ecological impact categories for this research, LCA guidance documents and case studies
were consulted. The resulting list of ecological impact categories is shown in Table 3-1. The
impacts have been categorized by their mechanism of action, mainly whether they result from
chemical or nonchemical pollutants or from resource depletion.
3.2 Human Health Impacts
Potential human health impacts of NMP as used in painting and depainting operations
result primarily from the use stage of its life cycle, where workers may be directly exposed to
NMP emissions. Additional human health impacts may result from emissions released during
the production and disposal stages of the life cycle. To establish a baseline set of human health
impact categories for this research, LCA guidance documents and case studies were consulted.
The resulting list of human health impact categories is shown in Table 3-2. Again, the impacts
have been categorized by their mechanism of action, mainly whether they result from chemical or
nonchemical pollutants.
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Table 3-1. Ecological Impact Categories Related to Chemical and Nonchemical Stressors
and Resource Depletion
Chemical
Nonchemical
Resource Depletion
Global warming
Ozone depletion
Acid deposition
Photochemical oxidant
formation
Tropospheric ozone
Aquatic toxicity
Eutrophication
Visibility alterations
pH alterations
Chemical/biological
content alteration
Oxygen depletion
Aquifer contamination
Land use
Ionizing radiation
Heat
Noise
Environmental disturbance
-habitat alteration
-physical change to water
-physical change to soil
Regional climate change
Species change
-composition
-total diversity
Nonrenewable
Fossil fuels
Minerals
Renewable
Water
Renewable energy
Agricultural resources
Wilderness resources
Table 3-2. Human Health Impact Categories Related to Chemical and Nonchemical
Stressors
Chemical
Nonchemical
Human carcinogen
Inhalation toxicity
Irritant (eye, lung, skin, gastrointestinal)
Respiratory system effects
Central nervous system effects
Mutagenicity
Developmental toxicity
Allergenicity
Blood dyscrasias
Odors
Cardiovascular system effects
Reproductive effects
Behavioral effects
Bone effects
Renal effects
Heat
Noise
Light
Nuisance
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4.0 Data Review
A joint literature search was conducted for NMP and PC. Both of these chemicals are
components of PC2, which is used in depainting. This section discusses the literature search and
summarizes the available information on NMP's physical and chemical properties,
environmental fate and transport, and toxicity. However, Tables 4-1 and 4-2 are inclusive of
both NMP and PC.
4.1 Sources
Research Triangle Institute (RTF) conducted an extensive literature search for NMP and
PC. In addition to searching online databases, manufacturers were contacted, government reports
were located, and an Internet search was conducted. Results of the literature and Internet
searches are summarized in the following sections.
4.1.1 Literature Search
A literature search was performed using the databases listed in Table 4-1. The databases
were searched from 1990 to the present using N-methyl-pyrrolidone and propylene carbonate as
key words. The number of relevant articles found in each database is listed in Table 4-1.
Table 4-1. Literature Search for NMP and PC
Name of Database
Database Topic
Number of
Articles Found
MEDLINE
Enviroline
Wilson Applied Science and
Technology Abstracts
Pollution Abstracts
Environmental Bibliography
NTIS: National Technical
Information Services
Ei Compendex
World Surface Coatings
Abstracts
Health and medicine
Environmental subjects
Science and technology
Pollution topics
Environmental subjects
Government technical reports
Engineering
Coating, paints, inks
6
1
54
1
6
2
86
14
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A second search was performed using the following key words related to NMP and PC:
greenhouse, global warming, acid rain, smog, photochemical, ozone, air dispersion, air aging, air
transport, aquatic, plant life, eutrophication, visibility, weather, thermal, alterations, oxygen
depletion, aquifer, thermal change, and oxygen depletion. Table 4-2 lists the databases searched,
the dates searched, and the number of articles found in each database.
Table 4-2. Specific Topic Literature Search for NMP and PC
Name of Database
Database Topic
Number of
Articles Found
Dates Searched
Meteorological and
Geoastrophysical Abstracts
Enviroline
GeoArchive
WATEKNET
Water Resources Abstracts
GEOBASE
BIOSIS
Aquatic Sciences and Fisheries
Abstracts
Environmental Bibliography
MEDLINE
CANCERLIT
PsycINFO
TOXLINE
EMBASE
IAC Health and Wellness
Database
Meteorological and 0
environmental
Environmental subjects 2
Geosciences 0
Water topics 0
Water resource topics 8
Ecology 0
Biological abstracts 22
Marine and freshwater 0
environments
Environmental subjects 6
Health and medicine 14
Cancer 3
Pyschology, health 0
Toxicological literature 34
Biomedical literature 49
Health 1
June 1970-1997
August 1975-1997
August 1974-1997
1971-1997
August 1967-1997
August 1980-1997
September 1969-1997
September 1979-1997
October 1974-1997
November 1966-1997
September 1975-1997
October 1967-1997
August 1965-1997
August 1974-1997
1976-1997
Government sources and manufacturers contacted included the EPA Office of Pollution
Prevention and Toxics (OPPT), the Toxic Substances Control Act (TSCA) Administrative
Record, the U.S. Coast Guard, BASF Corporation, Huntsman Specialty Chemical, ISP, and
ARCO Chemical Company.
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OPPT provided the following reports:
Lifecycle Analysis and Pollution Prevention Assessment for N-Methylpyrrolidone
(NMP) in Paint Stripping (U.S. EPA, 1993)
Initial Screening of Chemical Ingredients and Substitutes in Consumer and Small
Shop Paint Stripper Formulations (U.S. EPA, n.d.)
Consumer/Small Shop Paint Stripping Use Cluster AR-161 Risk Management Report
Public Comment Draft (U.S. EPA, 1996b).
A report entitled Consumer Paint Stripping Products Containing N-Methylpyrrolidone -
Draft Final Report (Eastern Research Group Inc., n.d) was obtained from the Administrative
Record, File AR-075, in the TSCA Non-Confidential Information Center.
Although the U.S. Coast Guard is currently evaluating alternatives to using methylene
chloride for small aircraft paint stripping, no information on NMP is now available.
BASF Corporation in Wyandotte, MI, could not provide a list of companies using its
NMP-based products; however, it did provide the following reports:
1,4-Butanediol Derivatives Flow Chart (BASF, n.d. a)
Acetylenic Chemicals Reaction Flow Chart (BASF, n.d. b)
Formulating Paint Strippers with N-Methylpyrrolidone (BASF, 1990)
N-Methylpyrrolidone Application Profile - Immersion Paint Stripping (BASF, n.d. c)
N-Methylpyrrolidone Biodegradability (BASF, n.d. d)
ซ N-Methyl Pyrrolidone (NMP Technical Tips): Chemical Warfare Resistant Coatings
(CARC) Removal from Metal Surfaces (BASF, n.d. e)
ป N-Methyl Pyrrolidone (NMP Technical Tips): Reclaiming or Recycling of NMP
(BASF, n.d. f)
ป l-Methyl-2-Pyrrolidone, Material Safety Data Sheet (BASF, 1997)
ป Replacement ofMEK with N-Methylpyrrolidone in Coatings Plant Resin Clean Up
Operations (BASF, n.d. g)
ซ Surface Tension Modification ofNMP-Based Paint Strippers (BASF, n.d. h)
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N-Methylpyrrolidone (NMP): Formula for Success (BASF, n.d. i).
In addition, BASF's New Jersey branch supplied the following data sheet:
Data Sheet for NMP (EJCJD, n.d).
The data sheet summarizes all toxicity testing of NMP performed by U.S. and
international companies. The report lists the type of test (i.e., LD50), animal species, value,
method, year, test substance, result, and source. The two (primary) sources for test data were
BASF AG Ludwigshafen and ISP Europe GUILDFORD. Most of the comments in the results
were in German, and most of the data have not been published.
Huntsman Specialty Chemical in Houston, TX, provided the following information:
Test Procedures for the Degradability and Bacterial Toxicity of Chlorinated
Hydrocarbon Replacements (Kayser et al., n.d.)
Permeability of Commercial Solvents Through Living Human Skin (Ursin et al.,
1995).
ISP supplied a toxicity overview for NMP (ISP, n.d.), and ARCO Chemical Company,
Newtown Square, PA, provided data sheets covering environmental fate and ecological toxicity
of NMP (ARCO, n.d.).
4.1.2 Internet Search
Several Internet searches were conducted to gather environmental profile data for NMP.
The following keywords were used for the searches: n-methylpyrrolidone, n-methyl-2-
pyrrolidone, NMP, methylene chloride substitution, methyl ethyl ketone substitution, solvent
replacement, solvent substitution, depainting solvents, painting solvents, aircraft depainting,
paint removal, health effects (n-methylpyrrolidone), environmental effects (n-
methylpyrrolidone), ecological effects (n-methylpyrrolidone), radome depainting, paint stripping,
toxicity (n-methylpyrrolidone), aerospace painting, and aerospace depainting. Table 4-3 provides
a list of Internet sites that were found for NMP.
4-4
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Table 4-3. Internet Searches for NMP Environmental Profile Data
Title Address
Type of Information
N-Methylpyrrolidone (NMP) -
General Information
http ://sage.rti.org/nmp_gen.htm
List of 286 Chemicals Added to the http://rtk.net/E8209T660
Toxics Release Inventory (TRI)
Hazardous Substances Data Bank
(HSDB)
Worksafe Australia
Health and Safety Page
National Fire Protection
Association (NFPA) Chemical
Hazard Labels
Site Specific Procedures for
Carcinogens
Chemfinder
Chemical Sampling Information
DuPont NonWovens Chemical
Abstract Number Search Page
http://www.allette.com.au/worksafe/haz/AZ/
NMethyl2pyrrolidone.htm
http://ntp-db.niehs.nih.gov/
NTP_Reports/NTP_Chem_H&S/
NTP_Chem8/Radian872-50-4.txt
http://www.orcbs.msu.edu/chemical/nfpa/
hazardinformation(m).html
http://www.cc.rochester.edu/Admin/EHAS/
sitespec/sts_carc.htm
http://chemfinder.camsoft.com/
http://www.osha-slc.gov/
ChemSamp_data/CH_254480.html
http://www.dupont.com/Tyvek/protective-
apparel/Chemical-Data/cas.htm
The Environmental Chemicals Data http://ulisse.etoit.eudra.org/cgibin_ecd/
Information Network (ECDIN) inter_query
Data Bank
Background
Background
Background, populations
at risk (workers), toxicity
(lab animal data), use,
and environmental fate
and transport
Populations at risk
(workers)
Populations at risk
(workers)
Populations at risk
(workers)
Populations at risk
(workers)
Physical and chemical
properties
Physical and chemical
properties
Physical and chemical
properties
Identification, physical
and chemical properties,
production and use,
legislation and rules,
occupational health and
safety, toxicity,
concentrations and fate in
the environment,
detection methods,
hazards and emergency
response
(continued)
4-5
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Table 4-3. (Continued)
Title
Address
Type of Information
Welcome to Fisher Scientific
http://www.fisherl.com/fb/
itv?16..f97.4.msf0007.69.1..
National Center for Manufacturing http://solvdb.ncms.org
Sciences
N-methylpyrroIidone (NMP) -
Representative Material Safety
Data Sheet (MSDS) Summaries
Guide to National Institute for
Occupational Safety and
Health/Occupational Safety and
Health Administration
(NIOSH/OSHA) Air Sampling
Methods
The Carcinogenic Potency Project
8(e) Triage Chemical Studies
Database
Envirosense Solvent Substitution
Data Systems
Fiberglass Mold Cleaning
General Information
P2 in Plastics Manufacturing
P2 Tech Archive
Air Force Link Official web site
of the U.S. Air Force
Chem Systems Inc. Special
Reports
National Library of Medicine
PubMcd
http://clean.rti.org/nmp_msds.htm
http://www.skcinc.com/NIOSHl/
FELE1120.HTM
http://potency.berkeley.edu/pub/tables/
hybrid.rodents.text
http://www.epa.gov/docs/8e_triag
http://es.inel.gov/ssds/ssds.html
http://clean.rti.org/fibr_gen.htm
http://nben.org.p2tech/plas tics.html
http://gopher.great-lakes.net:2200/
R4935...80-lm/mailarc/p2tech
http://www.af.mil/index.html
http://www.chemsystems.com/
special.htm#butanediol
http://ncbi.nlm.nih.gov/PubMed
Physical and chemical
properties, hazards
identification,
toxicological information,
regulatory information
Physical and chemical
properties, health and
safety data, regulatory
information,
environmental fate data
Physical and chemical
properties, toxicity data,
reactivity data
Physical and chemical
properties
Toxicity (lab animal data)
Toxicity (lab animal data)
Use
Use
Use
Use
Use
Background
Toxicity (human data)
(continued)
4-6
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Table 4-3. (Continued)
Title
Address
Type of Information
National Library of Medicine
Internet Grateful Med
SERDP Keyword Search
DoD Defense Environmental
Network and Information
eXchange
Agency for Toxic Substances and
Disease Registry (ATSDR) World
Wide Web (WWW) Document
Text Search
Environmental Health Perspectives
Search Form
National Institute of Standards and
Technology (MIST) Chemistry
WebBook
University of Utah MSDS Archive
Solvent Handbook Database
System-M-PYROL
Environmental Science Center
Experimental Log P (octanol/water
partition coefficient) Database
Physical Properties Database
(PHYSPROP)
http://igm.nrm.nih.gov
http://www.hgl.com/SERDP/keyword/
defaulthtm
http://es.inel.gov/program/p2dept/defense/
denix.html
http://atsdrl.atsdr.cdc.gov:8080/
atsdrhome.html
http://ehpnetl.niehs.nih.gov/docs/
ehp_search.html
http://webbook.nist.gov/chemistry
http://www.chem.utah.edU/MSDS/M/
l-METHYL-2-PYRROLIDONE
http://wastenot.inel.gov/shds
http://esc.syrres.com/~ESC/database.htm
Commercially available database
Toxicity (human data)
Use
N/A
N/A
Toxicity
Thermochemical and
thermophysical properties
Physical and chemical
properties, toxicity data,
reactivity data
Air efficiency data, paint
stripping data, paint
corrosion data, recycling
data, cleaning efficiency
data, corrosion data,
compatibility data
Experimental log p
(octanol/water partition
coefficient)
Chemical structures,
names, and physical
properties
(continued)
4-7
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Table 4-3. (Continued)
Title
Address
Type of Information
Environmental Fate Database
(EFDB)
Commercially available database
Toxic Substances Control Act Test Commercially available database
Submission (TSCATS) Database
Chemical Pointer File
Commercially available database
Compilation of Ozone Depletion http://esc.syrres.com/~ESC/ODPGWP.htm
Potentials (ODP) and Global
Warming Potentials (GWP)
Atmospheric Oxidation Database http://esc.syrres.com/~ESC/aopexp.htm
DcfenseLINK (Links to Army, Air http://www.defenselink.mil
Force, Navy, and Marine Corps
homepages)
N/A = no information on NMP was available at this site.
Environmental fate and
exposure data including
adsorption,
bioconcentration,
biodegradation,
dissociation constant,
effluent concentrations,
monitoring, occupational
concentrations, and
photo-oxidation
Unpublished technical
reports submitted by
industry concerning
health effects,
environmental effects,
and environmental fate
Regulatory information,
toxicity, environmental
fate and transport
N/A
N/A
N/A
4.2 Physical and Chemical Properties
N-methylpyrrolidone is a slow-evaporating, highly polar, aprotic, organic solvent. Its
molecular formula is CjHgNO. It is a colorless, low-viscosity liquid with a faint amine odor and
is fully miscible with water. N-methylpyrrolidone is the lactam of 4-methylaminobutyric acid
and a very weak base. Commercial NMP has a typical pH of 8.0 to 9.5 (BASF, 1997). NMP
exhibits high solvent activity over a variety of resins commonly used in paint and coating
formulations including acrylic and polyurethane systems as well as lacquer-type systems. The
rate of solvent activity can be increased by increasing the temperature of the formulation
containing NMP or the substrate to be stripped (BASF, 1990). Table 4-4 presents the physical
and chemical properties of NMP.
4-8
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Table 4-4. NMP Physical and Chemical Properties
Physical State1
Liquid
Appearance1
Odor1
Vapor density1
Boiling point (Fahrenheit)2
Freezing point (Fahrenheit)2
Specific gravity2
Viscosity (cP)2
Vapor pressure (rnmHg)2
Surface tension (dynes-cm2)2
Flash point (Fahrenheit)2
Explosion limit % (upper)2
Explosion limit % (lower)2
Evaporation rate1
Molecular weight3
Solubility (water)3
Solubility (95% ethanol)3
Solubility (acetone)3
Solubility (dimethyl sulfoxide [DMSO])3
Typical pH4
Autoignition temperature (Fahrenheit)5
Reactivity5
Percent volatiles by volume6
Clear colorless liquid
Mild, amine-like
3.4 (air =1)
395.6
-11.92
1.033
1.666
0.341
40.7
197.6
9.5
1.3
0.03 (butyl acetate = 1)
99.13
>=100 mg/mL @ 20 ฐC (rad)
>=100 mg/mL @ 20 ฐC (rad)
>=100 mg/mL @ 20 ฐC (rad)
>=100 mg/mL @ 20 ฐC (rad)
8.0 to 9.5
518
Stable. Avoid heat, fire, and ignition sources.
Incompatible with strong oxidizing or
reducing agents.
100
(continued)
4-9
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Table 4-4. (Continued)
Physical State1
Liquid
Bulk density7
Critical temperature (K)8
Critical pressure (Pa)8
Experimental log p (octanol/water partition
coefficient)9
1.028
7.218 E+02
4.780 E+06
-0.38
References
1 Fisher Scientific, 1996. http://www.fisherl.com/fb/itv?16..f97.4.msf0007.69.1...
l-Methyl-2-pyrrolidinone Material Safety Data Sheet.
2 National Center for Manufacturing Sciences. http://solvdb.ncms.OTg/SOLV-DB: -
Methylpyrrolidone.
3 Health and Safety Page. 1991. http://ntp-db.niehs.nih.gov/NTP_Reports/ NTP_Chem_
H&S/NTP_Chem8/Radian872-50-4.txt. NTP Chemical Repository (Radian Corporation,
August 29, 1991): N-Methyl-2-pyrrolidone.
4 N-Methylpyrrolidone (NMP) - General Information. 1997. http://sage.rti.org/nmp_gen.htm.
N-Methylpyrrolidone.
5 N-methylpyrrolidone (NMP) - Representative MSDS Summaries. 1997.
http://clean.rti.org/nmp_msds.htm. N-Methylpyrrolidone.
6 J.T. Baker Chemical, n.d.
7 BASF Corporation, 1997.
8 Zhao, Renhong. U.S. EPA Systems Analysis Branch.
9 Environmental Science Center Experimental Log P (octanoywater partition coefficient)
Database. http://esc.syrres.com/~ESC/database.htm.
4.3 Environmental Fate and Transport
N-methylpyrrolidone is highly mobile in soil (soil adsorption coefficient estimate of 9.6)
but unlikely to absorb to sediment or suspended organic matter to any significant degree. It may
slowly volatilize from dry soil but not from moist soil. N-methylpyrrolidone also has a low
volatility from water because of its high solubility and low Henry's law constant. Its estimated
half-life for volatilization from a model river (1 m deep, 1 m per flow, 3 m per s wind speed) is
2,335 days. N-methylpyrrolidone has a calculated bioaccumulation factor (BCF) of 0.16 and is
unlikely to bioconcentrate significantly in aquatic organisms or the food chain (ARCO, n.d.).
Biodegradation occurs under aerobic conditions in aquatic or terrestrial environments;
however, a short log phase may occur. The half-life of NMP was determined to be 4.0, 8.7, and
11.5 days in clay, loam, and sandy soils, respectively. Rapid gas-phase reactions with hydroxyl
radicals would be expected in the atmosphere (estimated t1/2 = 5.2 hours). Significant removal by
4-10
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reaction with ozone is not likely. Reactions in the atmosphere can also be described as slow
oxidation to hyperoxides, accelerated by light (ARCO, 1997).
An aerobic degradation measurement of 73 percent biological oxygen demand (BOD) in
28 days was determined for NMP. This test consisted of incubation of 100 mg/L with 30 mg
activated sludge for 4 weeks. Other biodegradability findings reported by ARCO (1997) include
the following:
95 percent removal in 2 weeks (static die-away system, sewage sludge inoculum)
95 percent removal in 7 days (average) (semicontinuous, activated sludge)
> 98 percent removal in 24 hours (210-mg/L initial concentration, sewage sludge
inoculum)
94 percent removal chemical oxygen demand (COD) screening study, 1-day lag (150-
mg/L initial concentration, activated sludge inoculum)
>98 percent removal 18-hour retention (model flow-through treatment, 300 mg/L
activated sludge)
>90 percent removal screening study, lag of 3-5 days (static, sewage sludge).
The biodegradability of NMP was tested using a variety of test methods. All test results
indicated that NMP is practically fully biodegradable. Table 4-5 summarizes these test results
(BASF, n.d. d).
Table 4-5. NMP Biodegradability Test Results
Test
Dissolved Organic Carbon-Degradation (%)
Coupled-Units
Zahn-Wellens
Mm
Sturm
OECD-Screening
99
98
95
97
99
An NMP biodegradability test conducted by the University of Stuggart designed to
simulate as closely as possible conditions in a publicly owned treatment works (POTW)
produced the following results (BASF, n.d. d):
4-11
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a) A municipal sewage treatment plant (POTW) has a base capacity to eliminate
spontaneously up to 10 mg/L without adaptation.
b) The adaptation to higher NMP concentrations is very fast.
c) No deadaptation occurs if the supply of NMP is interrupted for 1 week.
d) If a POTW is not overloaded, virtually complete elimination of NMP in domestic
sewage can be expected.
NMP was found to be nontoxic to most aquatic life and readily degraded by typical wastewater
treatment plant organisms.
Another biodegradability test, conducted by the Singapore Department of Scientific
Services, examined the biodegradability of NMP using a static die-away system and a
semicontinuous activated sludge system. The NMP concentrations of the influent for the
activated sludge process were around 100 ppm. Results of the die-away test showed that 95
percent biodegradability of NMP was obtained after a 2-week period of incubation and, therefore,
was readily degradable in a static system. Ninety-five percent biodegradability was
accomplished after 5 days of incremental acclimation in the semicontinuous activated sludge test.
It was also found, however, that the metabolite of the degradation was a carbonyl compound
having a significant COD that could not be broken down completely under these conditions
(Chow and Ng, 1983).
A study was conducted to examine the possibility of biochemical oxidation of NMP at
high starting concentrations (up to 1,200 mg/L) and to determine the aeration time necessary to
attain a required degree of cleanup. Testing was performed in an aeration tank with a capacity of
20 to 50 L per tank. Sludge containing NMP at concentrations of 200 to 400 mg/L was adapted
in the tanks for 2 weeks. Later, the NMP concentration was increased to 600 to 800 mg/L and
then to 1,200 mg/L. The results of this study indicate that in concentrations up to 1,200 mg/L
NMP does not adversely affect active sludge and can be subjected to biochemical destruction in
aeration tanks. In addition, sorption dominates over bio-oxidation in the initial NMP removal
period (Ivanov et al., 1989).
4.4 Toxicity
NMP has undergone fairly extensive toxicity testing under TSCA; however, much of the
data is unpublished. Several summaries were obtained from the manufacturers that provide a
brief overview of the toxicology data. In general, NMP has a low order of acute, subchronic, and
chronic toxicity. It is mildly irritating to skin but is moderately to severely irritating to the eyes.
The available data indicate that NMP is not likely to be mutagenic or carcinogenic, but there is
some evidence of reproductive and developmental effects in laboratory animals at high doses.
The following sections present an overview of the available information.
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4.4.1 Human Data
Very few reports on human exposure and toxicity were located for NMP. The available
studies examined skin irritation in workers, acute effects in volunteers, pharmacokinetics, and
skin permeability.
Leira et al, 1992. Irritant Cutaneous Reactions to N-Methyl-2-Pyrrolidone (NMP).
After 2 days of work with NMP, 10 of the 12 workers in an Safety electrotechnical
company in Norway experienced acute irritant contact dermatitis of the hands. The material
safety data sheet (MSDS) of a Norwegian sales firm contained no information on cutaneous
hazards, but the MSDS of an American producer of NMP stated the risk of severe dermatitis
(blister, edema, cracking, redness) upon prolonged or repeated contact. This information was
based on unpublished case reports where undiluted NMP had been used for cleaning purposes
over prolonged periods without cutaneous protection. Butyl rubber was identified as the best
glove material to prevent NMP penetration. Polyvinyl acetate (PVA) was listed as a suitable
material as well, but latex, neoprene, nitrile, and polyvinyl chloride (PVC) were not
recommended. In this case, latex glove use was continued, with cotton gloves worn underneath
to prevent moisture buildup, and the gloves were changed hourly. With this precaution, skin
problems ceased. This study indicates that NMP is a stronger skin irritant than previously
reported.
Akesson andPaulsson, 1997. Experimental Exposure of Male Volunteers to N-Methyl-2-
Pyrrolidone (NMP): Acute Effects and Pharmacokinetics of NMP in Plasma and Urine.
Six male volunteers were exposed for 8 hours on 4 different days to 0, 10, 25, and 50
mg/m3 NMP. The subjects were exposed two at a time in an exposure chamber with an air
turnover rate of 20 per hour. There was an exposure free period of about 5 minutes after 2, 4,
and 6 hours of exposure for examination and biological sample collection. NMP exposure was
assessed by four consecutive 2-hour sampling periods in the personal breathing zone of each
subject. Blood samples were taken before the start of the exposure, immediately after the
exposure, and 16 hours after the exposure. Changes in nasal volume and airway resistance were
measured. The geometry of the nasal cavity was assessed by continuous acoustic rhinometry
before exposure and 2, 4, 6, and 8 hours after the start of exposure. In the 10 to 50 mg/m3
exposure range, no subjective self-reported sensations of eye, nasal, or respiratory irritation
occurred. Pulmonary functions and nasal cavities were not affected by NMP exposure. N-
methylpyrrolidone was readily eliminated in the urine. The mean half-lives were 4 hours and 4.5
hours for plasma and urine, respectively. Only 2 percent was excreted in urine as unmetabolized
NMP. At the end of the exposure, there was a close correlation between exposures and the
plasma concentration and urinary excretion of NMP, which indicated that biological monitoring
of exposure to NMP or risk from NMP is possible. Results indicate that NMP is a mild irritant.
4-13
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Ursin et at, 1995. Permeability of Commercial Solvents through Living Human Skin.
The steady-state rate of permeation of commercial solvents through living human skin
was measured. Skin was removed from healthy females during plastic surgery of the breast. The
samples were thinned by removing the dermal tissue from the epidermis and then stretched to a
thickness of 300 to 600 ,um. Each piece of surgically removed skin usually provided sufficient
material to run nine permeation experiments. The permeability rate of NMP was determined to
be 171 g/m2h, which was about three times faster than MEK and seven times faster than
methylene chloride. This study indicates that NMP is readily absorbed through human skin.
4.4.2 Laboratory Animal Data
Acute toxicity of NMP has been studied in rats, mice, guinea pigs, rabbits, and quail. The
reported oral lethal dose to 50 percent of test animals (LD50) ranged from about 3.5 to 7.5 g/kg,
indicating a very low order of acute toxicity (ISP, n.d.). Subchronic (ingestion and inhalation)
studies and reproductive and developmental studies have been conducted in a number of
laboratory animals. These studies are briefly reviewed below.
Bartsch etal, 1976. Acute Toxicity of Various Solvents in the Mouse and Rat.
Various solvents are frequently used to improve the solubility of poorly soluble
compounds in pharmacological and lexicological experiments. This study was conducted to
assess the toxicity of each solvent to avoid a false assessment of the compound being tested.
Nine different solvents, including NMP, were examined to find lethal dose levels in the mouse
and the rat. The solvents were administered into the tail vein and orally through a stomach tube
to a group of 10 animals (5 males and 5 females) of both mice and rats. The solvents were
administered in quantities such that at least 3 mortality values between 16 and 84 percent were
obtained. The three LDSO values for NMP in mice were 3.5 IV, 4.3 IP, and 7.5 PO. NMP's LD50
values for rats were 2.2 IV, 2.4 IP, and 3.8 PO. From these data, it was concluded that no more
than a quarter of the LD50 of the solvent should be used in pharmacological and toxicological
experiments to avoid interference between the substance under investigation and the solvent.
Becci et at, 1983. Subchronic Feeding Study in Beagle Dogs of N-Methylpyrrolidone.
This study was conducted to evaluate the toxicological effects of NMP following dietary
administration for 13 weeks to male and female dogs. Dose levels were 0,25,79, and 250 mg/kg
body weight per day. Dosage groups consisted of 6 male and 6 female dogs. Examinations
conducted to study possible toxicological and pathological effects included body weight gain and
food consumption; hematological and clinical chemical data; and ophthalmic, gross, and
histopathological examinations. A dose-dependent decrease in body weight and an increase in
platelet count correlating with increased megakaryocytes were noted. Serum cholesterol in males
4-14
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decreased with the increasing doses of NMP. Feeding NMP to dogs at levels of up to 250 mg/kg
body weight per day resulted in no statistically significant toxicological or pathological effects.
Malek et al, 1997. Repeated Dose Toxicity Study (28 Days) in Rats and Mice with N-
methylpyrrolidone (NMP).
The repeated dose toxicity of NMP was evaluated in a 28-day feeding study in rats and
mice. Groups of 5 male and 5 female rats each were fed either 0, 2,000, 6,000, 18,000, or 30,000
ppm NMP and groups of 5 male and 5 female mice each were fed either 0, 500, 2,500, 7,500, or
10,000 ppm. Compound-related mortality did not occur during the study in either sex of the rats.
Lower mean body weight values and body weight gain values (reflecting decreased food
consumption) were seen in male rats fed diets containing 18,000 ppm or greater NMP and female
rats fed diets containing 30,000 ppm NMP. Clinical chemical changes were also observed in the
rats at 18,000 ppm in males and at 30,000 ppm in both sexes, indicating possible compound-
related alterations in lipid, protein, and carbohydrate metabolism. No histopathological changes
in rats were judged to be directly related to NMP exposure. In the mice, cloudy swelling of the
epithelia of the distal parts of the renal tubuli was observed in 4 males and 3 females at 10,000
ppm and in 2 males at 7,500 ppm. Abnormal urine coloration was observed in mice at 2,500
ppm and above and in rats at 18,000 ppm and above. Although the urine discoloration was
compound-related, no adverse effects were noted in either species.
Engelhardt and Fleig, 1993. l-Methyl-2-Pyrrolidinone (NMP) Does Not Induce Structural
and Numerical Chromosomal Aberrations in Vivo.
N-methylpyrrolidone, a widely used industrial and commercial solvent, has been shown
through several studies to be neither a point mutagenic nor a clastogenic agent. However, it has
been found to induce aneuploidy in vitro using Saccharomyces cerevisiae. Aneuploidy is
associated with spontaneous abortions, congenital malformations, birth abnormalities, and
carcinogenesis; therefore, it poses a serious hazard to humans. Micronucleus tests and
chromosome analysis test were performed using male and female mice and Chinese hamsters,
respectively. In the micronucleus tests, doses of 3,800, 1,900, and 950 mg/kg NMP were given
to test groups. Animals in the highest dose group were observed 16, 24, and 48 hours after
treatment, while lower dosage groups were observed 24 hours after treatment. For the
chromosome analysis, 3,800 or 1,900 mg/kg NMP was given. Bone marrow was sampled after
24 hours in the lower dosage group and after 24 hours and 48 hours in the higher dosage group.
In the micronucleus tests, NMP did not increase the frequency of polychromatic erythrocytes
containing either small or large micronuclei, indicating that NMP has neither a clastogenic effect
nor a spindle poison effect in vivo. In the chromosome analysis tests, the administration of NMP
did not result in an increase in the number of mitoses containing structural chromosomal
alterations, numerical chromosomal alterations, or numerical chromosomal aberrations. NMP
did not reveal any clastogenic or aneugenic activity. Both NMP tests failed to show a mutagenic
4-15
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effect, the number of polychromatic etrythrocytes containing either small or large micronuclei
and the frequency of aberrant mitoses always falling in the range of the negative controls.
Hass et at, 1995. Developmental Toxicity of Inhaled N-Methylpyrrolidone in the Rat.
Fifty-five rats were mated and split into a control group (27 rats) and an experimental
group (28 rats). On days 4 through 20 of pregnancy, the rats were exposed for 6 hours per day to
clean air and to air containing the highest technically possible concentrations of NMP (about 165
ppm). The animals were observed daily after exposure for signs of toxicity. Body weight and
food consumption were recorded on days 4,7,14, and 21 of pregnancy. On day 21 of pregnancy,
rats were decapitated. The following data were recorded: weight of intact uterus; number of
corpora lutea; and number of implantations and fetuses alive, dead, or resorbed. The live fetuses
were weighed, their sex determined, and then examined for external malformations. No clinical
signs of maternal toxicity were seen during the exposure period. There were no statistically
significant differences between the two groups on the number of corpora lutea, implantations,
and resorptions or live fetuses per dam. A higher incidence of preimplantation loss and
significantly more dams with preimplantation loss were observed in the exposed group. The
mean fetal body weight in the litters was slightly lower in the exposed group but was not
statistically significant. There was an increase in delayed ossification observed among litters of
rats exposed to NMP. The number was statistically significant for cervical vertebrae and for
digital bones. Further studies are needed to assess the dose-response relationship as the
implications of the results of this study are that NMP may not be a harmless replacement for
other organic solvents.
Hass, 1990. Prenatal Toxicity of N-methylpyrrolidone in Rats: Postnatal Study.
Groups of pregnant rats were exposed to either 150 ppm NMP or to clean air 6 hours per
day on days 7 through 20 of gestation. After delivery, the development of the pups was
observed. Milestones such as pinnae development, incisor eruption, and eye opening were
recorded along with development of reflexes (surface righting, auditory startle, air righting) and
homing response. After weaning, 2 males and 2 females were selected for further testing. Onset
of puberty (vagina opening, complete separation of frenulum) and growth until day 100 were
recorded. The males were further investigated for motor ability, activity, learning, and memory.
The pups born to the exposed mothers had a lower mean body weight than the control group.
This difference in mean body weight persisted into adulthood. The exposed group also exhibited
delays in several developmental milestones and reflexes.
Bead et al, 1982. Teratogenicity Study of N-Methylpyrrolidone after Dermal Application to
Sprague-Dawley Rats.
In this dose range finding study, the dose levels of NMP used were 500, 1,100, and 2,500
mg/kg body weight per day. Rats were mated, 1 male to 1 female. After mating, 5 pregnant
females were assigned to each treatment group. On day 5 of gestation, an application site was
4-16
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prepared by carefully clipping the fur on the back of each animal. From days 6 to 15 of gestation,
material was spread over the skin and rubbed in. The test materials remained on the animals for
8 hours per day, at which time any residual material was removed. Body weights of the dams
were taken on days 0, 6, 9, 12, 15, and 20. The females were euthanized with chloroform on day
20 of gestation. In the teratogenicity study, the dose levels for NMP were 75, 237, and 750
mg/kg body weight per day. All procedures for this study were the same as for the dose range
finding study, except that each treatment group consisted of 25 females and each fetus was
examined for teratologic effects. Results of the dose range finding study showed that at all
dosage levels, treatment with NMP was associated with patches of dry skin at the application
area and a bright yellow color of the urine. At the high dosage level (2,500 mg/kg), all dams died
or spontaneously aborted prior to day 20 of gestation. At 1,100 mg/kg of NMP, all but 1 of the
66 fetuses were resorbed. At the low dosage level (500 mg/kg), NMP had no adverse effect on
pregnancy, dam body weights, implantations, or gestation when compared to negative controls.
Results of the teratology study showed that dams treated with NMP showed patches of dry skin,
the severity of which increased with the dose. Treatment with NMP at the highest dosage level
resulted in a decrease in the number of viable offspring, an increase in the mean number of
resorption sites per dam, and a decrease in the mean fetal weight. No effect on pregnancy,
implantation, or gestation was noted in the middle or low dosage levels of NMP. Fetuses in the
high dosage group exhibited an increased incidence of several skeletal abnormalities. Soft tissue
examinations revealed no dose-related differences in the type or frequency of anomalies observed
in fetuses from dams treated with NMP when compared to control groups.
Hass et at, 1994. Effects of Prenatal Exposure to N-methylpyrrolidone on Postnatal
Development and Behavior in Rats.
This study was conducted to assess the effects that prenatal exposure to NMP has on the
development of rats. Two groups of pregnant rats were exposed to either 150 ppm NMP or to
clean air for 6 hours a day on gestation days 7 through 20. There was no evidence of maternal
toxicity resulting from exposure to NMP. The only change attributable to NMP was a bright
yellow coloring of the urine from the rats in the exposed group. Litters from the exposed
mothers had a lower mean body weight, from birth throughout the preweaning period, than pups
in the control group. The exposed pups' physical development was delayed, and they were
significantly delayed in some recorded developmental milestones and in the ontogeny of the
surface righting reflex. There were no differences between the exposed and control groups for
the age of sexual maturation, motor function, activity level, and performance in learning tasks
with a low grade of complexity. However, performance was impaired in the exposed offspring in
more difficult tasks.
Solomon et al, 1995. l-Methyl-2-Pyrrolidone (NMP): Reproductive and Developmental
Toxicity Study by Inhalation in the Rat.
This study was conducted to assess the effect of prolonged exposure to NMP before and
during the reproductive period on reproductive and developmental processes. Rats used in the
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experiment were split into two groups. The first group of male and female rats served as the P0
generation. The second group of rats served as unexposed mates for the Fl generation. Rats
within the P0 group were distributed randomly into seven groups (10 males and 20 females per
group). At 34 days old, the rats were exposed to 10, 51, or 116 ppm NMP for 6 hours a day, 7
days a week. Males were exposed for a minimum of 100 days, while females were exposed for a
minimum of 106 days. At 119 days of age, each male was placed with 2 females from the same
treatment group. Pregnant females were not exposed to NMP from day 20 of gestation to day 4
postpartum. The produced offspring were designated as the Fl generation. On day 70
postpartum, 1 male and 1 female were selected from each litter to mate with the unexposed rats
from the previous group to produce an F2 generation. For the developmental phase, both male
and female rats inhaled 0 or 116 ppm NMP. Results of the study indicate that reproductive
performances did not differ between the exposure groups. Rats exposed to 116 ppm NMP did
have a detectable decrease in response to sound; however, they showed no other signs of NMP-
related toxicity. A slight decrease in fetal weight was recorded among the Fl offspring whose
parents both inhaled NMP at 116 ppm. No detectable or developmental effects appeared in the
10- or 51-ppm groups.
Lee et al, 1987. Toxicity of N-Methyl-2-Pyrrotidone (NMP): Teratogenic, Subchronic, and
Two-Year Inhalation Studies.
The toxicity of NMP was tested on rats in a teratogenic study, a 4-week inhalation study
and a 2-year inhalation study. La the teratogenic study, groups of 25 pregnant rats were exposed
to 0.1 and 0.36 mg/L of NMP in air for 6 hours a day on days 6 through 15 of gestation. A
control group was exposed to air in a similar chamber. During the first 3 days of exposure,
several of the rats experienced sporadic lethargy and irregular respiration. However, these signs
were not seen after that period or during the 10-day recovery period. NMP exposure did not
affect the pregnancy or embryonal growth rate. A 4-week inhalation study was conducted using
a total of 60 male and 60 female rats divided into four groups of 15 rats of each sex. These rats
were exposed to 0.1,0.5, and 1.0 mg/L NMP for 6 hours a day, 5 days a week, for 4 weeks. A
control group was treated under similar conditions using only air. Exposure was discontinued
after 10 days in the 1.0 mg/L group due to an excessive mortality rate. These rats had focal
pneumonia, bone marrow hypoplasia, and atrophy of lymphoid tissue in the spleen and thymus.
No clinical signs or pathological lesions were found in rats at the lower exposure levels. A third
group of rats was exposed to 0, 0.04, or 0.4 mg/L NMP for 6 hours a day, 5 days a week, for 2
years. There were no evident life-shortening toxic or carcinogenic effects observed in this group.
4.4.3 Toxicokinetics
N-methylpyrrolidone is well-absorbed from all three primary routes of exposure
(ingestion, inhalation, and skin). Following absorption, NMP is rapidly metabolized and
excreted in the urine. Studies in rats indicate that about 90 percent of the dose is eliminated
within 24 hours and studies in human volunteers indicate a plasma half-life of about 4 hours.
N-methylpyrrolidone is rapidly distributed to all major organs, but uptake is low. The highest
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tissue concentrations occur in the liver and intestines (about 2 and 3 percent of the total dose,
respectively). The major metabolic pathway is ring hydroxylation, and 5-hydroxy-N-
methylpyrrolidone is the primary metabolite (ISP, n.d.; Wells and Digenis, 1988). Several
toxicokinetic studies are reviewed below.
Akesson andjonsson, 1997. Major Metabolic Pathway for N-Methyl-2-Pyrrolidone in
Humans.
The metabolic pathway for NMP was studied in humans. Three male volunteers were
administered 100 mg NMP orally. All urine was collected during nine consecutive 24-hour
sampling periods. Gas chromatography/mass spectrometry (GC/MS) was used to identify and
quantify metabolites in the urine. The metabolites included NMP, 5-hydroxy-N-methyl-2-
pyrrolidone (5-HNMP), N-methylsuccinimide (MSI), and 2-hydroxy-N-methylsuccinimide (2-
HMSI) and were measured at levels of 0.8 percent, 44 percent, 0.4 percent, and 20 percent,
respectively. The increasing half-lives of NMP, 5-HNMP, MSI, and 2-HMSI suggest the '
existence of a metabolic pathway where NMP is first hydroxylated to 5-HNMP, then further
oxidized to MSI, and then hydroxylated to 2-HMSI. The half-lives for 5-HNMP, MSI, and 2-
HMSI in urine were approximately 4, 8, and 17 hours, respectively. One-third of the oral dose of
NMP was not found as any of the above compounds, which may reflect incomplete absorption
from the gastrointestinal tract or the presence of metabolites undetected by the assay.
RTI, 1991. Absorption, Distribution, Metabolism and Elimination of N-Methyl-2-Pyrrolidone
(NMP) in Rats after Oral and Dermal Administration.
The disposition of oral and dermal doses of 14C-labeled NMP was studied in 28 male
Fischer rats. Rats were given oral doses of NMP of 5 and 500 mg/kg by gavage. Oral doses of
NMP were mainly excreted in the urine, with 75 percent (plus or minus 3 percent) of the 500
mg/kg dose and 84 percent (plus or minus 3 percent) of the 5 mg/kg dose excreted in the first 24
hours post-dosing. Elimination of radioactivity in feces or as volatile components in breath was
low, and only 1.7 percent of the doses were converted into CO2. Dermally administered NMP
was absorbed very well and excreted primarily through the urine. About 50 percent of the 0.2
and 2.0 mg/cm2 doses and 75 percent of the 20 mg/cm2 dose were absorbed, suggesting that NMP
enhances its own absorption. Blood level equivalents of NMP in animals given a dermal
application of 240 mg NMP in a dose site of 12 cm2 rose to a maximum of 640 ^g-equivalents/g
blood at about 8 hours. At least four metabolites were present in the urine; little or no NMP was
excreted unchanged. The profile of urinary metabolites present after dermal exposures was
similar to those after oral administration. Up to 60 percent of the administered doses were
excreted as a single metabolite, 5-HNMP.
Akhter and Barry, 1985. Absorption through Human Skin oflbuprofen and Flurbiprofen;
Effect of Dose Variation, Deposited Drug Films, Occlusion and the Penetration Enhancer N-
Methyl-2-Pyrrolidone.
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The penetration of ibuprofen and flurbiprofen, nonsteroidal inflammatory agents, was
tested on cadaver skin using NMP as a penetration enhancer for the carboxylic acids. Strips of
Caucasian abdominal skin were mounted in glass diffusion cells. Ibuprofen and flurbiprofen at
three dose levels each were applied in 50 uL acetone. The penetration profile was monitored for
180 hours. During the first 60 hours, penetration was from acetone and from a deposited drug
film. One-hundred microliters of NMP was added toward the end of the experiment to cover the
skin. The addition of the NMP produced a sudden increase in the penetration rate of the
ibuprofen and flurbiprofen by changing the diffusional resistance of the membrane. The quantity
of drug permeating across the skin was increased due to the decreased loss of the drug to
evaporation.
Wells andDigenis, 1988. Disposition and Metabolism of Double-Labeled N-Methyl-2-
Pyrrolidinone in the Rat.
N-methylpyrrolidone is frequently used as a solvent in the formulation of pesticides and
as a solubilizing agent in parenteral and topical veterinary pharmaceutical products. Despite this,
the in vivo disposition of NMP in man or animals is largely unknown. This study was developed
to evaluate the disposition and metabolism of NMP in the rat. Specifically, the work was
designed to study the pharmacokinetics and tissue distribution of single- and double-labeled
NMP after a single intravenous dose in the rat and to identify the major metabolic pathways.
Male rats were anesthetized and their jugular veins were cannulated with tubing. Each rat was
injected with a 5.0-juCi dose of either [methyl-I4C]-, [ring-14C]-, or [4-3H]NMP in isotonic saline
(0.2 to 0.35 mL). For double-labeled radioisotopic studies, animals were coadministered 5.0 /j-Ci
of [4-3H]NMP and 2.5 /zCi of either [methyl-14C]- or [ring-14C]NMP. Urine and feces were
collected every 6 hours for the duration of the study. Expired air was collected for 24 hours
following dosing. A second group of rats was treated with single isotope doses of 8.0 /^Ci and
double-labeled isotope doses of 8.0 //Ci of [4-3H]NMP and 4.0 ^Ci of either [methyl-14C]- or
[ring-14C]NMP. Serial blood samples were withdrawn at the following times after dosing: 5,10,
15,20, 30,45, 60, 90, 120,240, and 360 minutes. In a third group, rats were anesthetized and
remained anesthetized throughout the study. Double-labeled isotope doses of 5.0 yuCi of [4-
3H]NMP and 2.5 //Ci of [ring-14C]NMP were administered through the jugular vein and the bile
duct. Bile was collected at the following times after dosing: 15, 30,45, 60, 75, 90, 105, 120,
150, 180, 210, and 240 minutes. After a single IV injection, NMP was rapidly distributed to
tissues and then showed a slow elimination profile from plasma, suggesting that NMP may be
slowly released from a storage deport such as fat. N-methylpyrrolidone was extensively
distributed to all the major organs, with appreciable amounts found in the liver and the kidneys at
6 hours. The major route of excretion of radioactivity was through the urine and accounted for
about 70 percent of the dose within 12 hours. After 24 hours, the cumulative excretion in urine
represented about 80 percent of the dose.
Midgley et al, 1992. Percutaneous Absorption of Co-Administered N-Methyl-2-
[14C]Pyrrolidinone and 2-[14C]Pyrrolidinone in the Rat.
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This study was designed to assess the oral route as a valid alternative to dermal
application for systemic toxicity studies of NMP and 2-pyrrolidinone (2-P). Oral doses of the
mixture in solution were given to 66 rats (33 of each sex) by gastric intubation. The doses were
equal to 112 mg NMP and 75 mg 2-P/kg body weight. Topical doses of the same mixture were
applied to 66 other rats on a shaven area of the animal's back. The treated area was covered with
aluminum foil to avoid oral ingestion of the topical dose. Blood was withdrawn from each
animal by cardiac puncture under halothane anesthesia followed by cervical dislocation to kill
them. Plasma, urine, cage washings, contents of expired air traps, occlusive dressing digests and
extracts, application-site washings, skin digests, and carcass digests were separately mixed with a
special scintillator for measurement of radioactivity. Concentrations of unchanged NMP and 2-P
were determined in the plasma of orally and topically dosed rats by high-performance liquid
chromatography (HPLC) with an online radioactivity detector. Radioactivity was excreted
predominately in the urine following either dermal or oral administration routes. At 2 hours after
oral dosing, plasma concentrations reached peak values and remained relatively uniform during 1
to 6 hours after application to the skin. This rate suggests constant percutaneous absorption
during this period. N-methylpyrrolidone was absorbed through the skin at a faster rate than 2-P,
and total percutaneous absorption was faster in females than in males. The oral route was
considered to be a valid alternative to the dermal route due to the extensive percutaneous
absorption and little first-pass metabolism of the two pyrrolidinones.
Wells et al, 1992. Isolation and Identification of the Major Urinary Metabolite ofN-
Methylpyrrolidone in the Rat.
Male rats were injected with either unlabeled NMP or a 5-^Ci dose of [methyl-14C]NMP
in isotonic saline. Unlabeled NMP in saline was coadministered with [methyl-14C]NMP to
achieve a dose of 45 mg/g. Urine was collected from 0 to 12, 12 to 24, and 24 to 48 hours after
dosing. Using GC/MS, 5-HNMP was identified as the major urinary NMP metabolite.
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5.0 Impact Assessment
This section reviews the available data on environmental fate and transport and toxicity to
determine potential impacts to human populations and the environment from exposure to NMP.
5.1 Human Populations at Risk
U.S. EPA (1993) has prepared an LCA for NMP in paint-stripping. Because of limited
data on NMP, much of the LCA was based on data for methylene chloride and extrapolated to
NMP based on known or expected differences in physicochemical characteristics, production
volume, method of use, and so on. No case reports for NMP releases were identified. According
to U.S. EPA (1993), NMP releases were not reported and recorded in the TRI database and no
TRI reports since 1993 were found for NMP.
Human populations at risk include workers who use NMP and residents who may be
exposed through contamination of water supplies, soil, air, or food or who may use NMP
products at home. Because of NMP's low volatility, inhalation exposures are expected to be low.
However, inhalation exposures can occur when used in a poorly ventilated area, when sprayed
on, and/or when NMP solutions are heated during use. Because NMP is readily absorbed
through the skin, dermal contact can be a significant exposure pathway. The U.S. EPA (1993)
LCA report indicated that workers involved in the manufacture of NMP or the use of NMP in
depainting operations and workers in consumer/small shop paint-stripping were at risk of
reproductive and developmental effects if personal protective equipment, particularly proper
gloves, was not worn. This report also concluded that risk from exposure to the general
population and to the environment under normal circumstances of manufacture and use is
minimal. Exposure from food is not likely to be significant because NMP does not
bioaccumulate and is biodegradable. However, NMP spills could pose a threat to ground water
and water supplies because of low soil adsorption and high solubility. Available case studies are
summarized below.
Beaulieu and Schmerber, 1991. M-Pyrol (NMP) Use in the Microelectronics Industry.
This study was conducted to establish a threshold limit value (TLV) for NMP.
Previously, no TLV had been set; however, the GAP Corporation had recommended a time-
weighted average (TWA) exposure of 100 ppm.
N-methylpyrrolidone is used in the microelectronics industry to strip phenolic residue
from packages and photoresist resins on wafer surfaces and as a vehicle for "die-coat"
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application. Occupational exposure and stack emission sampling for NMP vapor was performed
at two microelectronic fabrication facilities. Site A, constructed in 1979, was a class 100 (100
particles per cubic foot of air) wafer fabrication facility with better particle control achieved
through process microenvironments. Site B, built in 1985, was a class 10 control of particulate
matter in air in the wafer fabrication areas. Twenty-five air samples were collected from each
facility. Industrial hygiene evaluations were performed in the die-coat application areas, in the
NMP cleaning rooms, and in rooftop stack exhausts. Several conclusions were drawn from this
study. The manufacturer's recommended TLV of 100 ppm for NMP vapor is unacceptable.
Many of the employees developed headaches and chronic eye irritation at exposure levels of 0.7
ppm. This study indicates that semiconductor industry employees have typical exposures ranging
from 0.02 to 1.5 ppm NMP. The results of this study also indicate that employee exposure
should be controlled to less than 0.1 ppm through local exhaust ventilation, good work practices,
and the use of personal protective equipment.
Solomon et al, 1996. Stillbirth after Occupational Exposure to N-Methyl-2-Pyrrolidone.
A laboratory technician worked at a chemical manufacturing company in a multiroom
quality control (QC) laboratory, analyzing samples for production runs. The woman's
responsibilities included operating two atomic absorption spectrophotometers where she
dissolved each solid sample in NMP. During her pregnancy, the woman was given a half-face
air-purifying respirator in addition to her other protective equipment, which included a laboratory
coat, safety goggles, and latex gloves. At the 16th week of gestation, there was a spill of NMP at
work, which the woman cleaned up. The NMP dissolved the latex gloves, causing extensive
direct skin contact to her hands, including a break in the skin. Over the next 4 days, the woman
felt ill with malaise, headache, nausea, and vomiting. She was removed from work on sick leave
about 4 weeks after the incident and later returned to office duties with no further exposures to
NMP. By the 20th week of gestation, she had been exposed to NMP an average of 42 hours a
week. At 25 weeks' gestation, an ultrasound showed early intrauterine growth retardation, at
which the growth of the fetus corresponded with a 21-week gestational age. Five weeks later, no
fetal activity or fetal heart sounds were detected from the ultrasound. The patient was induced
and delivered a stillborn fetus. At 31 weeks of gestation, the fetus appeared to be at 29 weeks'
gestation. After leaving the exposed environment, the woman had a successful full-term
pregnancy without complication. A review of available literature found that NMP has
consistently been demonstrated to have fetotoxic effects on animals. N-methylpyrrolidone
adversely affects the fetus in all tested animal species at or slightly below levels that cause mild
signs of toxicity in adult animals. The effect is shown through fetal loss or delayed fetal
development. From this case and animal literature, NMP should be considered fetotoxic in
humans. Companies, and laboratories in particular, should have reproductive health policies in
effect that allow for nondiscriminatory voluntary removal of prospective parents in situations of
possible exposure.
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Anundi et al, 1993. High Exposures to Organic Solvents among Graffiti Removers.
This study was designed to measure the exposures to solvents and possible related health
effects among graffiti removers and to eventually promote the use of personal protection.
Twelve men participated in the study. The men ranged in age from 18 to 36 years and had
worked as graffiti removers between 3 months and 4.5 years. Their job involved removing
graffiti from underground stations by spraying solvent on the contaminated surfaces and
swabbing with a tissue or applying thickened solvent with a brush and washing with heated high-
pressure water spray. Organic solvents used to remove graffiti include dichloromethane (DCM),
NMP, trimethylbenzenes, and the glycol ethers dipropylenglycolmonomethylether (DPGME) and
propylenglycolmono-n-butylether (PGBE). The workers did not use respirator masks, and
gloves, when used, were made of leather and were frequently soaked with solvent. Four workers
were studied per day using a battery-operated personal air sampler. Air was aspirated at a flow
rate of 15 mL per minute through a charcoal tube and an XAD-2 tube. Fifteen-minute samples
were also collected during different work procedures with a pump flow rate of 150 mL per
minute. A questionnaire was filled out by each worker to assess previous occupations and
nonoccupational exposure to organic solvents, estimated use of the different cleaning products in
their present work, and use of protective equipment. High exposures of DGM were found among
the workers, with 50 percent of the workers exceeding the permissible exposure limit (PEL) for
this solvent. The highest short-term levels were up to 17 times the occupational limit value. N-
methylpyrrolidone is easily absorbed through intact skin and, therefore, should be seen as a
potential risk. Health effects most readily observed among graffiti removers consisted primarily
of irritative effects in the upper respiratory tract and the eyes. Workers were advised to use half-
mask respirators and also to protect their skin against spillage.
Zellers and Sulewski, 1993. Modeling the Temperature Dependence of N-Methylpyrrolidone
Permeation through Butyl- and Natural-Rubber Gloves.
Gloves selected for testing included one butyl-rubber glove and three other gloves
composed of either natural rubber or a blend of natural rubber with small percentages of nitrile
and neoprene rubbers. Permeation tests were conducted at four temperatures from 25 to 50 ฐC
using the ASTM F739-85 permeation test method. After 4 hours of exposure to NMP, the butyl-
rubber gloves showed no breakthrough at any temperature. For the remaining gloves, permeation
resistence decreased significantly as the temperature increased. Breakthrough values in the
gloves decreased by factors of 7 to 10 when temperatures were increased from 25 to 50 ฐC.
Temperatures were then extrapolated to 70 and 93 ฐC, the temperatures at which degreasing is
often performed. In all types of gloves, these temperatures yielded breakthrough values of less
than 2 minutes and less than 30 seconds, respectively. Gloves were also exposed to NMP at 25
ฐC and dried overnight. With the exception of the butyl-rubber gloves, low levels of NMP vapor
were detected off-gassing from the inner surfaces of the gloves. The results of this study suggest
that butyl-rubber gloves should be used for protection from NMP in cases where particulate
contamination (resulting from talc treatment of the gloves for adhesion inhibition) can be
tolerated.
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5.2 Natural Resources/Ecosystems
No specific reports of ecological damage following a spill of NMP were found. As
mentioned in the previous section, NMP was not included in TRI reporting. N-
methylpyrrolidone has been found to have a low to intermediate reactivity toward ozone (ARCO,
n.d.). It is biodegradable, does not bioaccumulate, and has a low acute toxicity to aquatic life.
The biological oxygen demand (BOD5), chemical oxygen demand (COD), and total organic
content (TOG) have been reported as 1,100 mg/mL, 1,600 mg/mL, and 600 mg/mL, respectively
(BASF, n.d d). Aquatic toxicity data are summarized below.
5.2.1 Aquatic Toxicity
Tests to determine the acute toxicity of NMP at concentrations of 100 mg/L for a period
of 4 days on guppies (Lebistes reticulatus) showed no toxic symptoms or effects (BASF, n.d. i).
The effective concentration (EC50) (48 hours) for the Golden orf (Leuciscus idus) was found to be
between 4,600 and 10,000 mg/L. The EC50 (96 hours) for the Rainbow trout (Oncorhynchus
mykiss) was found to be >500 mg/L. The EC50 (24 hours) for the water flea (Daphnia magna
Straus) was found to be >1,000 mg/L (BASF, n.d. d). Table 5-1 presents the findings of other
NMP aquatic toxicity tests (ISP, n.d.). N-methylpyrrolidone demonstrated low toxicity in all of
these tests,
Table 5-1. Results of NMP Aquatic Toxicity Testing
Species
LCSO (mg/L)
Sunfish
Fathead minnow
Trout
Water flea
Scud
Mud crab
Grass shrimp
GUDDV
0.81
l.l1
3.01
4.91
4.71
1.61
l.l1
1.32
1 GAP, 1979.
2 WeisbrodandSeyring, 1980.
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The EC50 (72 hours) for algae (Scenedesmus subspicatus) was found to be >500 mg/L.
For bacteria (Pseudomonas putidd), the EC50 (48 hours) was determined to be >9,000 mg/L
(BASF, n.d. d). The no-observed-effect concentration (NOEC) for NMP for algae and bacteria is
5,000 mg/L (ARCO, 1996).
5.2.2 Data Needs
Of the list of ecological impact categories presented in Section 3.1, data were available
for aquatic toxicity and oxygen depletion. Although NMP has shown reproductive and
developmental effects in mammals, reproductive studies in aquatic organisms were not available.
Other data needs include information concerning global warming potential, photochemical
oxidant (smog) formation, visibility alterations, weather alterations, pH alterations,
chemical/biological content alterations, aquifer contamination, land use, and natural resource
depletion.
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6.0 Environmental Regulations
The Chemical Abstracts Service (CAS) Number for NMP is 872-50-4.
N-methylpyrrolidone is currently listed in the Toxic Substances Control Act (TSCA) Inventory.
N-methylpyrrolidone is listed under the Superfund Amendments and Reauthorization Act
(SARA) 313 Title HI Emergency Planning and Community Right-to-Know Act (EPCRA),
Section 313(d)(2)(B), serious or irreversible chronic health effects. The effective date was
January 1, 1995, and the first reports were due July 1, 1996. A full discussion can be found in
the Federal Register dated November 30, 1994, Vol. 59, No. 229, pp. 61,432-61,485.
N-methylpyrrolidone is not listed under the Clean Air Act (CAA), the Comprehensive
Environmental Response, Compensation, and Liability Act (CERCLA), or the Resource
Conservation and Recovery Act (RCRA).
Table 6-1 provides a summary of the regulatory information related to NMP.
Table 6-1. Regulatory Information for NMP
Regulation
CAA
CERCLA
RCRA
SARA
CWA1
OSHA2
ACGIH3
IARC4
NIOSH5
NTP6
Applicability to NMP
Not listed
Not listed
Not listed
Yes
Not listed
Not listed
Not listed
Not listed
Not listed
Not listed
1 Clean Water Act
2 Occupational Safety and Health Administration
3 American Conference of Governmental and Industrial Hygienists
4 International Agency for Research on Cancer
5 National Institute for Occupational Safety and Health
6 National Toxicology Program
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In addition to the regulations listed in Table 7, NMP has a National Fire Protection
Association (NFPA) health hazard rating of 2 (BASF, 1997). This rating includes materials that
may cause temporary incapacitation or residual injury upon intense or continued exposure
without the provision of prompt medical treatment. Such treatment includes requiring the use of
respiratory protective equipment with an independent air supply. N-methylpyrrolidone has an
NFPA flammability rating of 2. This rating includes materials that must be exposed to relatively
high ambient temperatures before ignition occurs. Materials with this rating could produce
hazardous atmospheres with air under moderate heating or high ambient temperatures.
N-methylpyrrolidone has an NFPA reactivity rating of 0, meaning that the solvent is normally
stable, even under fire exposure conditions, and does not react with water.
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7.0 Summary
N-methylpyrrolidone is a general-purpose organic solvent with a wide variety of
industrial applications, including as an ingredient in process chemicals, engineering plastics,
coatings, and agricultural chemicals, and in paint stripping and cleaning operations (BASF,
n.d. i). This environmental profile was prepared to compile and review the available data
regarding potential impacts to human health and the environment from the use of NMP and
NMP-based formulations in painting and depainting DoD aircraft, vehicles, and other equipment.
This research included identifying case studies of NMP formulations in painting and depainting
operations or other applications with similar exposure scenarios, compiling toxicology and
environmental fate and transport data, and collecting analyses of environmental impacts.
Several case studies were identified and reviewed (see Section 2.2 and Appendix A).
These studies indicate that NMP formulations work slower and may be more expensive than
MEK or methylene chloride formulations, but they are generally effective, reduce emissions, and
reduce worker exposure.
Very little environmental impact data were available for NMP because TRI reporting has
not been required. N-methylpyrrolidone is highly mobile in soil and would be expected to leach
into ground water if spilled onto soil. It readily biodegrades in soil under aerobic conditions,
with estimated half-lives of 4 to 11.5 days, and in wastewater. Volatilization from soil and water
is slow; however, once released into the air, it reacts with hydroxyl radicals and degrades
(estimated tVfc of about 5 hours). N-methylpyrrolidone does not bioaccumulate in aquatic
organisms or in the food chain. The available aquatic data indicate a low order of toxicity.
Much of the toxicity information apparently has not been published; however, data are
available on acute toxicity, subchronic toxicity, chronic toxicity, mutagenicity, carcinogenicity,
and reproductive and developmental toxicity. N-methylpyrrolidone is readily absorbed through
all routes of exposure and is rapidly distributed, metabolized, and excreted in the urine. It is a
skin and eye irritant, and dermal contact should be avoided through use of proper gloves and
other personal protective equipment. Case reports of workers using NMP have shown acute
contact dermatitis after 2 days' exposure. Overall, the acute, subchronic, and chronic toxicity of
NMP is low. The LD50 in laboratory animals ranges from about 3.5 to 7.5 g/kg, and subchronic
studies in rodents have shown no adverse effects at concentrations as high as 6,000 mg/kg. The
available data suggest that NMP is not mutagenic or carcinogenic; however, it has produced
reproductive and developmental effects in several laboratory animal tests following high-dose
oral or inhalation exposures. In addition, at least one case report indicates that occupational
exposure to NMP may have resulted in a stillbirth.
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Populations at greatest risk from exposure include workers and individuals using NMP-
based products at home. Exposure to the general population should be minimal under most
circumstances unless a water supply has been impacted from a spill. At least one study has
indicated that the manufacturer's recommended threshold limit value (TLV) of 100 ppm is too
high and that NMP airborne concentrations should not exceed 0.1 ppm to protect against
headaches and chronic eye irritation. Although NMP is not readily volatilized, it can pose
inhalation hazards if adequate ventilation is not provided, if it is heated, or if it is sprayed.
Therefore, both respiratory and skin protection should be used to reduce exposure.
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Akesson, B., and K. Paulsson. 1997. Experimental exposure of male volunteers to N-methyl-2-
pyrrolidone (NMP): Acute effects and pharmacokinetics of NMP in plasma and urine.
Occupational and Environmental Medicine 54:236-40.
Akhter, S.A., and B.W. Barry. 1985. Absorption through human skin of ibuprofen and
flurbiprofen; Effect of dose variation, deposited drug films, occlusion and the penetration
enhancer N-methyl-2-pyrrolidone. /. Pharm. Pharmacol. 37:27-37.
Anundi, H., M-L. Lind, L. Friis, N. Itkes, S. Langworth, and C. Edling. 1993. High exposures to
organic solvents among graffiti removers. Int. Arch. Occup. Environ. Health. 65: 247-51.
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Bartsch, W., G. Sponer, K. Dietmann, and G. Fuchs. 1976. Acute toxicity of various solvents in
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Stripping.
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Resistant Coating (CARC) Removal from Metal Surfaces.
BASF Corporation, n.d. f. N-Methyl Pyrrolidone (NMP Technical Tips): Reclaiming or
Recycling of NMP.
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BASF Corporation, n.d. g. Replacement ofMEKwith N-Methylpyrrolidone in Coatings Plant
Resin Clean Up Operations.
BASF Corporation, n.d. h. Surface Tension Modification ofNMP-Based Paint Strippers.
BASF Corporation, n.d. i. N-Methylpyrrolidone (NMP): Formula for Success.
BASF Corporation. 1990. Formulating Paint Strippers with N-Methylpyrrolidone. BASF
Corporation, Mount Olive, NJ.
BASF Corporation. 1997. l-Methyl-2-Pyrrolidone Material Safety Data Sheet.
Beaulieu, H.J., and K.R. Schmerber. October 1991. M-pyrol (NMP) use in the microelectronics
industry. Appl Occup. Environ. Hyg. 6(10):874-79.
Becci, P.J., MJ. Knickerbocker, E.L. Reagan, R.A. Parent, and L.W. Burnette. 1982.
Teratogenicity study of N-methylpyrrolidone after dermal application to Sprague-Dawley
rats. Fundamental and Applied Toxicology 2(3-4):73-76.
Becci, P.J., L.A. Gephart, F.J. Koschier, and W.D. Johnson. 1983. Subchronic feeding study in
Beagle dogs of N-methylpyrrolidone. Journal of Applied Toxicology 3(2):83-86.
Chow, S.T., and T.L. Ng. 1983. The biodegradation of N-methyl-2-pyrrolidone in water by
sewage bacteria. Water Res 17:117-118.
Elion, J.M., J. Flanagan, J.H. Turner, J.T. Hanley, and E.A. Hill. October 1996. Pollution
Prevention Demonstration and Evaluation of Paint Application Equipment and Alternatives
to Methylene Chloride and Methyl Ethyl Ketone. EPA/600/SR-96/117.
Engelhardt, G., and H. Fleig. 1993. l-methyl-2-pyrrolidinone (NMP) does not induce structural
and numerical chromosomal aberrations in vivo. Mutation Research 298:149-55.
Eastern Research Group Inc. n.d. Consumer Paint Stripping Products Containing
N-Methylpyrrolidone - Draft Final Report obtained from the Administrative Record, File AR-
075, in the TSCA Non-Confidential Information Center.
Hass,U. 1990. Prenatal toxicity of N-methylpyrrolidone in rats: Postnatal study. Teratology
42(2):31A.
Mass, U., B.M. Jakobsen, and S.P. Lund. 1995. Developmental toxicity of inhaled N-
methylpyrrolidone in the rat. Pharmacology and Toxicology 76:406-409.
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Mass, U., S.P. Lund, and U. Eisner. 1994. Effects of prenatal exposure to N-methylpyrrolidone
on postnatal development and behavior in rats. Neurotoxicology and Teratology
16(3):241-49.
International Specialty Products (ISP), n.d.. Toxicity Overview N-Methyl Pyrrolidone
(M-Pyrol).
International Unified Chemical Information Database (IUCID). n.d.. Data Sheet for NMP.
Ivanov, Y.G., E.V. Rudakova, V.N. Chamaev, and Y.E. Matuskov. 1989. Biochemical clean-up
of wastewater containing N-methylpyrrolidone. Fibre Chem. 20(5):319-21.
J.T. Baker Chemical, n.d. l-Methyl-2-Pyrrolidinone - N-Methyl-2-Pyrrolidone Material Safety
Data Sheet.
Kayser, G., M. Koch, W. Erlmann, and W. Ruck. n.d.. Test Procedures for the Degradibility
and Bacterial Toxicity of Chlorinated Hydrocarbon Replacements. Translated from German
by the Ralph McElroy Company, Austin, TX.
Lee, K.P., N.C. Chromey, R. Culik, J.R. Barnes, and P.W. Schneider. 1987. Toxicity of N-
methyl-2-pyrrolidone (NMP): Teratogenic, subchronic, and two-year inhalation studies.
Fundamental and Applied Toxicology 9:222-35.
Leira, H.L., A. Tiltnes, K. Svendsen, and L. Vetlesen. 1992. Irritant cutaneous reactions to N-
methyl-2-pyrrolidone (NMP). Contact Dermatitis 27:148-50.
Malek, D.E., et al. 1997. Repeated dose toxicity study (28 days) in rats and mice with N-
methylpyrrolidone (NMP). Drug and Chemical Toxicology 20(l&2):63-77.
Met-Ed/Penelec Business and Industry, Technology Excellence Center (BITEC). 1996. BITEC
Assistance Report for James River Corporation, Lehigh Valley, PA (Concurrent
Technologies Corporation, Johnstown, PA).
Midgley, I., A.J. Hood, L.F. Chasseaud, C.J. Brindley, S. Baughman, and G. Allan. 1992.
Percutaneous absorption of co-administered N-methyl-2-[14C]pyrrolidinone and 2-
[14C]pyrrolidinone in the rat. Fd. Chem. Toxic. 30(l):57-64.
Research Triangle Institute. July 11, 1991. Absorption, Distribution, Metabolism and
Elimination of N-Methyl-2-Pyrrolidinone (NMP) in Rats after Oral and Dermal
Administration. Research Triangle Park, NC.
Solomon, G.M., E.P. Morse, M.J. Garbo, and D.K. Milton; Stillbirth after occupational exposure
to N-methyl-2-pyrrolidone. JOEM 38(7):705-13.
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Solomon, H.M., B.A. Burgess, G.L. Kennedy Jr., and R.E. Staples. 1995. l-methyl-2-
pyrrolidone (NMP): Reproductive and developmental toxicity study by inhalation in the rat.
Drug and Chemical Toxicology 18(4):271-93.
Ursin, C, C.M. Hansen, J.W. Van Dyk, P.O. Jensen, I.J. Christensen, and J. Ebbehoej. 1995.
Permeability of commercial solvents through living human skin. Am. Ind. Hyg. Assoc. J.
56:651-60.
U.S. EPA. n.d.. Initial Screening of Chemical Ingredients and Substitutes in Consumer and
Small Shop Paint Stripper Formulations. Washington, DC: Office of Pollution Prevention
and Toxics.
U.S. EPA. 1993. Lifecycle Analysis and Pollution Prevention Assessment for
N-Methylpyrrolidone (NMP) in Paint Stripping. Public RM2 Administrative Record
Document. Septembers. Washington,DC.
U.S. EPA. 1996a. Life Cycle Assessment for PC Blend 2 Aircraft Radome Depainter.
EPA/600/R-96/094. Washington, DC: Office of Research and Development.
U.S. EPA. 1996b. Consumer/Small Shop Paint Stripping Use Cluster AR-161 Risk Management
Report. Public Comment Draft Augusts. Washington, DC.
Wells, D.A., and G.A. Digenis. 1988. Disposition and metabolism of double-labeled [3H and
14C] N-methyl-2-pyrrolidinone in the rat. Drug Metabolism and Disposition 16(2):243-49.
Wells, D.A., A.A. Hawi, and G.A. Digenis. 1992. Isolation and identification of the major
urinary metabolite of N-methylpyrrolidinone in the rat. Drug Metabolism and Disposition
20(1): 124-26.
Zellers, E.T., and R. Sulewski. 1993. Modeling the temperature dependence of
N-methylpyrrolidone permeation through butyl- and natural-rubber gloves. Am. Ind. Hyg.
Assoc. J. 54(9):465-79.
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Appendix A
N-METHYLPYRROLIDONE CASE STUDIES
Depainting Case Studies
Pollution Prevention Demonstration and Evaluation of Paint Application Equipment and
Alternatives to Methylene Chloride and Methyl Ethyl Ketone
(J. M. Elion et. al, EPA/600/SR-96/117, October 1996).
Introduction
This research provides results of a demonstration of NMP as a possible alternative to
methylene chloride and MEK. The demonstration was conducted at the Marine Corps Logistics
Base in Albany, GA. This "demonstration took place where base vehicles were depainted by
methylene chloride through immersion. For this demonstration, NMP was chosen to replace
methylene chloride because it effectively removed CARCs in laboratory tests, is nonflammable,
and is not classified as an HAP by the EPA. If employed, this substitution would potentially
reduce HAPs at the base by 11 percent from 1992 levels.
Results and Discussion
To accommodate the NMP, an existing immersion tank was retrofitted by adding
plumbing to heat the tank with steam and a recirculating pump to provide enough agitation to
ensure a uniform temperature throughout the bath. An adjacent rinse tank required a pump to
draw recycled NMP for rinsing stripped parts. Finally, a vacuum distillation unit was installed to
reclaim used solvent from the stripping bath and to provide recycled NMP for rinsing. After
initial water testing, the tank was emptied and filled with an initial charge of 38, of the 208-L
barrels of technical-grade NMP. An additional 10 barrels were added later in the test.
The NMP, when heated to 66+6 ฐC, was able to remove multiple layers of CARC and
strip parts to the bare metal within 3 to 4 h. The heated NMP was able to successfully remove
Plastisolฎ, a plastic coating, from battery tie-down brackets. These parts were previously
stripped in a hot alkaline bath, followed by scraping and blasting to remove the coating. Also,
NMP was able to soften epoxy-based topcoats, but removal usually required overnight soaking.
From this study, NMP substitution for methylene chloride would potentially reduce HAPs
at the Marine base by 11 percent from 1992 levels.
Disadvantages of using NMP include the following: (1) NMP must be heated to be
effective, and (2) NMP is subject to reporting under SARA.
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The anmialized costs for NMP stripping are lower than for methylene chloride stripping,
but implementation requires high capital investment.
Surface Tension Modification of NMP-based Paint Strippers (W.C. Walsh, BASF
Corporation, Chemicals Division, Mount Olive, NJ).
Introduction
Solvents traditionally used in paint strippers include methylene chloride, methanol,
acetone, and MEK. In comparing these products with NMP-based paint removers, the primary
tradeoffs are stripping speed versus solvent inhalation and product cost versus usage cost. NMP-
based paint removers work at a slower rate but have dramatically lower vapor pressures, thus
reducing the chances of solvent inhalation. In addition, by lowering the surface tension of these
NMP formulas, the time required for their use may be decreased by as much as 40 percent.
Results and Discussion
Five NMP-based formulas, ranging in weight percent content from 12 to 80 percent, were
reviewed in this study to determine their effectiveness as paint strippers. All of these
formulations demonstrated good paint-stripping ability in the removal of commonly used paints
and coatings. During testing, performance data were developed on the ability of these products
to strip acrylic latex, alkyd, polyurethane, and epoxy coatings from wood substrates. They were
applied to test substrates by both brush and roller and given sufficient time to penetrate the
coating. Characteristics evaluated in this study included work area solvent concentrations,
material recyclability, waste generation, waste disposal, and stripping cost.
One method of judging the relative risk of inhalation is by comparing the ratios of
equilibrium vapor concentrations (EVCs) to PELs (8-h average) for each solvent. Ratios for the
NMP formulations ranged from 3 to 26 compared to the ratios for the conventional solvents,
which ranged from 320 to 900.
The modified NMP blends were tested against the original formulas, as well as against
Zip-Strip, a common methylene chloride-based product, to observe the time required to lift
various coatings from wood substrates at room temperature. The resultant stripping times,
ranging in minutes, are shown in Table A-l.
Even after reducing the time required to strip urethane enamel and household epoxy, the
NMP formulas were slower than the methylene chloride product. N-methylpyrrolidone works
slower, but it provides the user a working environment containing less solvent vapor.
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Table A-l. Comparative Stripping Times (minutes)
Paint type
Alkyd (3 layers)
Urethane enamel (2 layers)
Household epoxy (2 layers)
Acrylic latex (2 layers)
Urethane finish (1 layer)
NMP-baseda stripping times, min.
5-8
19-110
9-24
7-8
4-100
Zip-Strip stripping times, min.
2.0
2.0
1.5
2.0
1.5
a Results for modified and unmodified formulations.
A significant amount of the spent stripper is potentially a reusable solvent. If a sufficient
volume of thickened residue were isolated, a filter press could be used to separate the spent
solvent. This solvent could then be recycled through distillation and reused.
Results from this research show that a relatively minor amount of the stripper will
evaporate from the substrate, even after 25 h. After 3 h, 98 percent of the stripper formulation
remained on the surface. Waste disposal of the stripped paint/solvent residue, as well as any
paper cloth debris, was packaged in a thick-walled polyethylene or polyvinylidene chloride bag.
Appendices attached to the report describe sample preparation and surface coverage
comparison calculations.
In the study, the volume of the NMP blend required for a single application was
approximately 38 percent less than that required for Zip-Strip. This amount represents a
substantial savings in the actual material required to strip any given surface area.
Initial Screening of Chemical Ingredients and Substitutes in Consumer and Small Shop Paint
Stripper Formulations (Sherry Wise, Regulatory Impacts Branch, Economics, Exposure and
Technology Division, Office of Pollution Prevention and Toxics, U.S. Environmental
Protection Agency, Washington, D.C., June, 1994).
Introduction
This report contains information on chemical ingredients of commercially available paint
stripper products used to remove paint and other finishes by consumer do-it-yourselfers or small
shop operators (e.g., furniture restorers and refinishers). Coatings in the evaluations included
alkyd enamels, latex semigloss enamels, flat acrylic latexes, spar varnishes, urethane varnishes,
latex exterior enamels, interior vinyl acrylics, epoxies, marine paint, and marine varnish.
A-3
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Results and Discussion
NMP-based strippers accounted for 12 percent of the products reviewed, or a total of 9
products. Three of the 9 products reported NMP concentrations of 20 to 80 percent, 21 to 30
percent, and greater than 67 percent, by weight.
The evaluation results showed that NMP was satisfactory in possibly stripping most
paints. However, the NMP products required slightly longer times to achieve effective stripping
compared with methylene chloride. In Wood Magazines (1992), NMP-based products performed
less than satisfactorily compared with products containing methylene chloride but better than
products based on dibasic ester (5 of 7 finishes) and caustics (also 5 of 7 finishes).
Appendix B used a range of methodologies to evaluate the paint strippers. Some
consumer-oriented evaluations select a single representative stripping application and test the
performance of several retail formulations. Others simulate a variety of coating removal
situations (by using different types of coatings and substrates) and test both commercial products
and laboratory formulations. Some tests vary the cure time and exposure of the coating and try to
correlate stripping effectiveness with these variables.
Eight NMP-based strippers were rated below methylene chloride-based products on all
coatings but above ATM strippers (mixtures of acetone and/or toluene and/or methanol), with the
exception of enamel, where both NMP and ATM received an average score of 2.4. Average
ratings were between 2.4 and 2.9 on the 1- to-4 scale.
N-methylpyrrolidone was the fastest of the "safe" products (15 minutes to more than 1
hour, depending on the concentration of NMP). Each NMP-based product also had a slight odor
and was nonflammable. However, they were expensive, costing nearly twice as much as
methylene chloride removers. They can also cause dizziness and nausea after prolonged
exposure.
Other Studies - Cleaning
Replacement ofMEK -with N-Methyl Pyrrolidone (NMP) in Coatings Plant Resin Clean Up
Operations (W.C. Walsh, BASF Corporation, Chemicals Division, Mount Olive, NJ).
Introduction
This research discusses work conducted by a manufacturer of high-solids, oven-cured,
clear-coat, and base-coat coatings for Original Equipment Manufactures (OEM) automotive and
heavy equipment, as well as for some industrial applications, to evaluate replacing its MEK
cleaning solvent with NMP systemwide. It was anticipated that the cleaning system at the plant
would maintain the same standard of cleanliness throughout all stages of the coating production,
while using a chemical that created a lower amount of organic emissions. In addition to this,
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NMP was selected because of its heat-stable molecular structure, making it an ideal candidate for
recycling through distillation processes. , '=
Results and Discussion
MEK was used at this facility to clean up small reactors and to process holding tanks,
transfer lines, large blending tanks, transfer pumps, production floors, spray guns, and returnable
tote tanks. However, as MEK was continually used to solvate the more complex resin systems,
the amounts of MEK evaporating also increased. But, NMP's volatility is not as great as MEK
and, therefore, NMP does not evaporate as quickly as MEK.
Testing was conducted over a 10-month period to evaluate the capability of NMP to
replace MEK as a cleaning solvent in the manufacturing facility. Results from the study showed
that over a 10-month period there was a 5-fold decrease in MEK emissions from the facility and
that cleaning costs rose by 40 percent over total MEK costs. But, this increase was due to the
inexperience of the facility in initially using NMP. The total volume of cleaning solvent passing
through the plant decreased by 39 percent, 69 percent of which could be accounted for by the
decreases in virgin MEK purchases. Also, the total volume of MEK passing through the plant
decreased by almost 72 percent.
Met-Ed/Penelec Business and Industry, Technology Excellence Center (BITEC), BITEC
Assistance Report for James River Corporation, Lehigh Valley, PA (Concurrent Technologies
Corporation, 1450 Scalp Avenue, Johnstown, PA, May 1996).
Introduction
James River Corporation manufactures both wax-coated paper and plastic (high-impact
polystyrene polymer) drinking cups at its Lehigh Valley, PA, facility. The plastic cups are
manufactured using aluminum thermoforming tools, with up to 100 vent holes in each tool.
These tools were removed and placed in an immersion tank filled with Tower 19 paint thinner, a
mixture of 80 percent toluene and 20 percent acetone, for 15 to 30 minutes and then allowed to
air-dry. Once dry, the vent holes were manually probed to remove the accumulated polystyrene
using a drill bit.
James River originally used solvent-based chemicals to clean the aluminum
thermoforming tools. Due to health and safety concerns, these chemicals were replaced by an
ultrasonic cleaning system using aqueous chemicals. The aqueous chemicals proved to be
unsatisfactory for the tool-cleaning application.
James River's goal was to replace the Tower 19 paint thinner with a safer, low volatile
organic compound (VOC) cleaning chemical, preferably by using the ultrasonic cleaning system.
Thus, the objective of this study was to conduct a bench-scale test of three alternative solvents to
A-5
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evaluate their overall performance in the ultrasonic cleaning system. Factors such as cleaning
quality and drying time were evaluated and recommendations were made based on these results.
Results and Discussion
Several soiled aluminum thermoforming tools were submitted for testing. Each contained
a buildup of styrene residue in the vent holes. A test plan was developed to evaluate the
following alternative paint-stripping solvents:
NMP
Ethyl lactate
Oxysol.
The bench-scale ultrasonic cleaning unit was too small to accommodate the size of some
of the parts from James River, so 4-oz. souffle cups were used to hold the parts. The cups had to
be rotated during the cleaning test. The parts were immersed at ambient temperature for
approximately 15 to 20 minutes and subjected to ultrasonic energy. The unit provides 110 W of
sonic power at 85 kHz and holds approximately half a gallon. After cleaning, the parts were
visually inspected and the drying time noted. James River's goal was to achieve a 15-minute
drying time.
Based on the visual examination, NMP was the most effective of the three cleaners tested,
removing residues from recessed areas and small holes. N-methylpyrrolidone also did not emit
obvious odors during testing; however, drying times were relatively high. Some parts were still
wet after drying for 20 to 25 minutes at ambient temperature.
At the time, NMP was available for approximately $2.35/lb or approximately $1,000 to
$l,150/55-galdrum.
A-6
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