M&O Management and operating
MAC Maximum admissible concentration
MAP Model accreditation plan
MCCEM Multi-chamber concentration and exposure model
MCL Maximum Contaminant Level
MCLGs Maximum contaminant level goals
MDC Minimum detectable concentration
MDL Method detection level
MEDLARS Medical literature analysis and retrieval system
MEOW Maximum envelope of water; maximum envelope of winds
MERS Mobile emergency response support
MF Microfiltration
MFL Million fibers per liter
MICE Methods information communications exchange
MINTEQA2 Metal speciation for equilibrium for surface and groundwater
MIPS Map and Image Processing System
MIS Management Information System
MMU Minimum mapping unit
MMWR Morbidity and Mortality Weekly Report [CDC]
MOA Memorandum of Agreement
MOC MERS Operations Center, FEMA
MOE Margin of exposure
MOFAT Multi-phase flow and transport
MOS Margin of safety
MOU Memorandum of understanding
MP Melting point
MPC Maximum permissible concentration
MPN Maximum probable number
MPRSA Marine Protection, Research and Sanctuaries Act
MQC Minimum quantifiable concentration
MRDL Maximum residual disinfection levels
MRLC Multi-Resolution Land Characteristics Consortium
MSDS Material safety data sheets
MSL Mean sea level
MSS Multi-Spectral Scanner
MT Mitigation Directorate, FEMA; Montana
MTBE Methyl-t-butyl ether
MTD Maximum tolerated dose
MUD Metropolitan utilities district
MULTIMED Multimedia exposure assessment model
MUTA Mutagenicity
MWD Metropolitan Water District of Southern California
NAAQS National Ambient Air Quality Standards
NACE National Association of Corrosion Engineers
NADB National Air Data Branch
NAFTA North American Free Trade Agreement
NALC North American Landscape Characterization (USEPA, USGS)
NAPIS National Agricultural Pest Information System
NARL National Air and Radiation Laboratory
NAS National Academies of Science
NASA National Aeronautics and Space Administration
NATICH National Air Toxics Information Clearinghouse
NAWAS National warning system
NAWQA National Water Quality Assessment (USGS)
NBII National Biological Information Infrastructure
NBS National Biological Service
NCAT National catalog database
NCC National Computing Center
NCCDPHP National Center for Chronic Disease Prevention & Health Promotion, CDC
NCEH National Center for Environmental Health, CDC
NCHS National Center for Health Statistics, CDC
NCIC Nonconfidential Information Center
NCID National Center for Infectious Diseases, CDC
NCP National contingency plan
NCWS Noncommunity water system
ND None detected
NDCDB National Digital Cartographic Data Base
NDMS National Disaster Medical System
NDPD National Data Processing Division
NDWAC National Drinking Water Advisory Committee
NECC National Emergency Coordination Center, FEMA
NEDS National Emission Data System
NEIC National Enforcement Investigations Center
NEMA National electrical Manufacturers Association
NEPA National Environmental Policy Act
NERC National Ecology Research Center (Ft. Collins, CO)
NESC National Environmental Supercomputing Center
NESHAP National emission standards for hazardous air pollutants
NETA National Environmental Training Association
NEXRAD Next generation of radar
NF Nanofiltration
NFPA National Fire Protection Association
NHANES National Health and Nutrition Examination Survey
NHC National Hurricane Center
NIH National Institutes of Health
NIOSH National Institute of Occupational Safety and Health
NIPDWR National Interim Primary Drinking Water Regulations
NIST National Institute of Standards and Technology
NLLAP National Lead Laboratory Analytical Proficiency
NLM National Library of Medicine
NMD National Mapping Division
NOA Notice of arrival
NOAA National Oceanic and Atmospheric Administration
NOAEL No observed adverse effect level
NOM Natural organic matter
NPDES National Pollution Discharge elimination System
NPDWR National Primary Drinking Water Regulation
NPIRS National pesticide information retrieval system
NPL National priority list
NPS Nonpoint sources; National Park Service
NPSC National Process Serving Center, FEMA
NPTN National Pesticide Telecommunications Network
NRC National Response Center
NSDI National Spatial Data Infrastructure
NSDWR National secondary drinking water regulations
NSF National Sanitation Foundation; National Science Foundation
NSTC National Science and Technology Council
NTC National Teleregistration Center, FEMA
NTIS National Technical Information Service
NTNC Nontransient noncommunity water system
NTP National Toxicology Program
NTNCWS Non-transient, non-community water system
NTU Nephelometric turbidity unit
NTZ Nitazoxanide
NVFEL National Vehicle and Fuel Emissions Laboratory
NVOAD National voluntary organizations active in disaster
NWI National Wetlands Inventory (USFWS)
NWS National Weather Service
NWSFO National Weather Service Forecasting Office