P.29 

ATSDK - Minimal Risk Levels for Hazardous Substances (MRLs) 

ATSDR 

AGENCY FOR TOXIC SUBSTANCES 

ANO DISEASE REGISTRY 

RELATED RESOURCES 

PDF for Printing (37k) 

CONTENTS 

Narrative 

MRL List 

ATSDR RESOURCES 

Division of Toxicology 

Toxicological Profiles 

Page 1 of .11 

Docket No. A-79-15 

ItemNo.XlI-I-50 

Search | Index | Home | Glossary | Contact Us 

Minimal Risk Levels (MRLs) 

for 

Hazardous Substances 

The Comprehensive Environmental Response, Compensation, and 

Liability Act (CERCLA) [42 U.S.C. 9604 et seq.], as amended by the 

Superfund Amendments and Reauthorization Act (SARA) [Pub. L. 99-

499], requires that the Agency for Toxic Substances and Disease 

Registry (ATSDR) develop jointly with the U.S. Environmental 

Protection Agency (EPA), in order of priority, a list of hazardous 

substances most commonly found at facilities on the CERCLA National 

Priorities List (NPL) (42 U.S.C. 9604(i)(2)); prepare toxicological 

profiles for each substance included on the priority list of hazardous 

substances, and to ascertain significant human exposure levels (SHELs) 

for hazardous substances in the environment, and the associated acute, 

subacute, and chronic health effects (42 U.S.C. 9604(i)(3)); and assure 

the initiation of a research program to fill identified data needs 

associated with the substances (42 U.S.C. 9604(i)(5)). 

The ATSDR Minimal Risk Levels (MRLs) were developed as an initial 

response to the mandate. Following discussions with scientists within 

the Department of Health and Human Services (HHS) and the EPA, 

ATSDR chose to adopt a practice similar to that of the EPA's Reference 

Dose (RfD) and Reference Concentration (RfC) for deriving substancespecific health guidance levels for non-neoplastic endpoints. An MRL is 

an estimate of the daily human exposure to a hazardous substance that is 

likely to be without appreciable risk of adverse noncancer health effects 

over a specified duration of exposure. These substance-specific 

estimates, which are intended to serve as screening levels, are used by 

ATSDR health assessors and other responders to identify contaminants 

and potential health effects that may be of concem at hazardous waste 

sites. It is important to note that MRLs are not intended to define 

clean-up or action levels for ATSDR or other Agencies. 

The toxicological profiles include an examination, summary, and 

interpretation of available toxicological information and epidemiologic 

evaluations of a hazardous substance. During the development of 

toxicological profiles, MRLs are derived when ATSDR determines that 

reliable and sufficient data exist to identify the target organ(s) of effect 

or the most sensitive health effect(s) for a specific duration for a given 

route of exposure to the substance. MRLs are based on noncancer health 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
P.30 

ATSDR - Minimal Risk Levels for Hazardous Substances (MRLs) Page 2 of 11 

effects only and are not based on a consideration of cancer effects. 

Inhalation MRLs are exposure concentrations expressed in units of parts 

per million (ppm) for gases and volatiles, or milligrams per cubic meter 

(mg/m3) for particles. Oral MRLs are expressed as daily human doses in 

units of milligrams per kilogram per day (mg/kg/day). Radiation MRLs 

are expressed as external exposures in units of millisieverts. 

ATSDR uses the no-observed-adverse-effect-level/uncertainty factor 

(NOAEL/UF) approach to derive MRLs for hazardous substances. They 

are set below levels that, based on current information, might cause 

adverse healdi effects in the people most sensitive to such substanceinduced effects. MRLs are derived for acute (1-14 days), intermediate 

(>14-364 days), and chronic (365 days and longer) exposure durations, 

and for the oral and inhalation routes of exposure. Currently MRLs for 

the dermal route of exposure are not derived because ATSDR has not 

yet identified a method suitable for this route of exposure. MRLs are 

generally based on the most sensitive substance-induced end point 

considered to be of relevance to humans. ATSDR does not use serious 

health effects (such as irreparable damage to the liver or kidneys, or 

birth defects) as a basis for establishing MRLs. Exposure to a level 

above the MRL does not mean that adverse health effects will occur. 

MRLs are intended to serve as a screening tool to help public health 

professionals decide where to look more closely. They may also be 

viewed as a mechanism to identify those hazardous waste sites that are 

not expected to cause adverse health effects. Most MRLs contain some 

degree of uncertainty because of the lack of precise toxicological 

information on the people who might be most sensitive (e.g., infants, 

elderly, and nutritionally or immunologically compromised) to effects of 

hazardous substances. ATSDR uses a conservative (i.e., protective) 

approach to address these uncertainties consistent with the public health 

principle of prevention. Although human data are preferred, MRLs often 

must be based on animal studies because relevant human studies are 

lacking. In the absence of evidence to the contrary, ATSDR assumes that 

humans are more sensitive than animals to the effects of hazardous 

substances that certain persons may be particularly sensitive. Thus the 

resulting MRL may be as much as a hundredfold below levels shown to 

be nontoxic in laboratory animals. When adequate information is 

available, physiologically based pharmacokinetic (PBPK) modeling and 

benchmark dose (BMD) modeling have also been used as an adjunct to 

the NOAEL/UF approach in deriving MRLs. 

Proposed MRLs undergo a rigorous review process. They are reviewed 

by the Health Effects/MRL Workgroup within the Division of 

Toxicology; and expert panel of external peer reviewers; the agency 

wide MRL Workgroup, with participation from other federal agencies, 

including EPA; and are submitted for public comment through the 

toxicological profile public comment period. Each MRL is subject to 

change as new information becomes available concomitant witii 

updating the toxicological profile of the substance. MRLs in the most 

recent toxicological profiles supersede previously published levels. To 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
P.31 

ATSDR - Minimal Risk Levels for Hazardous Substances (MRLs) Page 3 of 11 

date, 120 inhalation MRLs, 189 oral MRLs and 6 extemal radiation 

MRLs have been derived. A listing of the current published MRLs by 

route and duration of exposure is provided as follows. 

ATSDR Contact Person for MRLs: 

Dr. Selene Chou 

Division of Toxicology 

Agency for Toxic Substances and Disease Registry 

1600 Clifton Road, Mailstop E29 

Atlanta, Georgia 30333 

Telephone: 404-498-0705 

E-Mail: cjc3@cdc.gov 

Note: Information is in landscape format. Please use scroll bar on the bottom ofthe screen to 

access all the information. You can also search the index of substances quickly by using the 

"Find" button on your web browser. For printouts, please use the PDF format. The PDF 

format requires Adobe Acrobat Reader, which can be downloaded free from the Adobe **"> 

web site. 

Name 

ATSDR MINIMAL RISK LEVELS (HRLs) 

January 2003 

Route 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Oral 

Oral 

Inh. 

Oral 

Oral 

Duration 

Int. 

Acute 

Int. 

Oir. 

Int. 

Acute 

Int. 

Chr. 

Acute 

Acute 

Int. 

Chr. 

Acute 

Chr. 

Int. 

Acute 

Chr. 

Int. 

Int. 

MRL 

0.6 mg/kg/day 

26 ppm 

13 ppm 

13 ppm 

2 mg/kg/day 

0.00005 ppm 

0.000009 ppm 

0.0005 mg/kg/day 

0.1 ppm 

0.1 mg/kg/day 

0.01 mg/kg/day 

0.04 mg/kg/day 

0.002 mg/kg/day 

0.00003 mg/kg/day 

2.0 mg/kg/day 

1.7 ppm 

0.3 ppm 

0.3 mg/kg/day 

10 mg/kg/day 

Factors 

300 

9 

100 

100 

100 

100 

1000 

100 

10 

100 

1000 

100 

1000 

1000 

30 

30 

10 

100 

100 

Endpoint 

Hepatic 

Neurol. 

Neurol. 

Neurol. 

Hemato. 

Ocular 

Resp. 

Hemato. 

Neurol. 

Develop. 

Repro. 

Hemato. 

Develop. 

Hepatic 

Neurol. 

Resp. 

Resp. 

Other 

Hepatic 

ACENAPHTHENE 

ACETONE 

ACROLEIN 

ACRYLONITRILE 

ALDRIN 

ALUMINUM 

AMMONIA 

ANTHRACENE 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
P.32 

ATSDR - Minimal Risk Levels for Hazardous Substances (MRLs) Page 4 of 11 

ARSENIC 

ATRAZINE 

BENZENE 

BERYLLIUM 

BIOALLETHRIN 

BIS(CHLOROMETHYL) ETHER 

BIS(2-CHLOROETHYL) ETHER 

BORON 

BROMODICHLOROMETHANE 

BROMOFORM 

BROMOMETHANE 

CADMIUM 

CARBON DISULFIDE 

CARBON TETRACHLORIDE 

CESIUM 

CHLORDANE 

CHLORDECONE 

CHLORFENVINPHOS 

CHLORINE DIOXIDE 

Provisional Oral 

Oral 

Inh. 

Oral 

Oral 

Inh. 

Inh. 

Oral 

Oral 

Oral 

Inh. 

Oral 

Oral 

Inh. 

Oral 

inh. 

Oral 

Rad. 

Inh. 

Oral 

Oral 

Oral 

inh. 

Acute 0.005 mg/kg/day 

Chr. 0.0003 mg/kg/day 

Acute 0.01 mg/kg/day 

10 

3 

Gastro. 

Dermal 

100 Body Wt. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Int. 

int. 

Acute 

Chr. 

Acute 

Chr. 

Acute 

Int. 

Chr. 

Int. 

Chr. 

Chr. 

Acute 

Acute 

int. 

Acute 

int. 

Acute 

Chr. 

Int. 

Chr. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Chr. 

Int. 

0.05 ppm 

0.004 ppm 

0.002 mg/kg/day 

0.0007 mg/kg/day 

0.0003 ppm 

0.02 ppm 

0.01 mg/kg/day 

0.04 mg/kg/day 

0.02 mg/kg/day 

0.6 mg/kg/day 

0.2 mg/kg/day 

0.05 ppm 

0.05 ppm 

0.005 ppm 

0.003 mg/kg/day 

0.0002 mg/kg/day 

0.3 ppm 

0.01 mg/kg/day 

0.2 ppm 

0.05 ppm 

0.02 mg/kg/day 

0.007 mg/kg/day 

4 mSv 

1 mSv/yr 

0.0002 mg/m3 

0.00002 mg/m3 

0.001 mg/kg/day 

0.0006 mg/kg/day 

0.0006 mg/kg/day 

0.01 mg/kg/day 

0.0005 mg/kg/day 

0.0005 mg/kg/day 

0.002 mg/kg/day 

0.002 mg/kg/day 

0.0007 mg/kg/day 

0.001 ppm 

300 

90 

300 

300 

100 

1000 

1000 

1000 

1000 

100 

100 

100 

100 

100 

100 

Tiiimiino. 

Neurol. 

Gastro. 

Develop. 

Resp. 

Body Wt. 

Develop. 

Hepatic 

Renal 

Neurol. 

Hepatic 

Neurol. 

Neurol. 

Neurol. 

Gastro. 

10 Renal 

30 

300 

300 

100 

300 

100 

3 

3 

100 

1000 

1000 

100 

100 

100 

100 

100 

1000 

1000 

1000 

Neurol. 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Develop. 

Other 

Hepatic 

Hepatic 

Develop. 

Hepatic 

Hepatic 

Neurol. 

Renal 

Renal 

Neurol . 

•Tnnwuno. 

Neurol . 

300 Resp . 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
ATSD R - Minimal Risk Levels for Hazardous Substances (MRLs) Page 5 of 11 

CHLORITE Oral Int. 0.1 mg/kg/day 30 Neurol 

CHLOROBENZENE 

CHLOR0DIBROMOMETHANE 

CHLOROETHANE 

CHLOROFORM 

Oral Int. 0.4 mg/kg/day 100 Hepatic 

CHLOROMETHANE 

CHLORPYRIFOS 

CKROMIUM(VI), AEROSOL MISTS 

CHROMIUM(VI), PARTICULATES 

COBALT 

COPPER 

CRESOL, METACRESOL, ORTHOCRESOL, PARACYANIDE, SODIUM 

Oral Acute 0.04 mg/kg/day 

Chr. 0.03 mg/kg/day 

Inh. Acute 15 ppm 

Oral Acute 0.02 mg/kg/day 

Oral Acute 0.05 mg/kg/day 

Oral Acute 0.05 mg/kg/day 

Oral Acute 0.05 mg/kg/day 

Oral int. 0.05 mg/kg/day 

CYCLOTBTRAMETHYLENE TETRANITRAMINE Oral Acute 0.1 mg/kg/day 

(HMX) Int. 0.05 mg/kg/day 

CYCLOTRIHETHYLENETRINITRAMINE (RDX) Oral Acute 0.06 mg/kg/day 

Int. 0.03 mg/kg/day 

DDT, P,P'-

DEX.TAMETHRIN 

DI(2-ETHYLHEXYL)PHTHALATE 

DI-N-BUTYL PHTHALATE 

Oral Acute 0.0005 mg/kg/day 

Int. 0.0005 mg/kg/day 

Oral Acute 0.002 mg/kg/day 

Oral Int. 0.1 mg/kg/day 

Chr. 0.06 mg/kg/day 

Oral Acute 0.5 mg/kg/day 

1000 

1000 

Renal 

Hepatic 

Inh. 

Oral 

Inh. 

Oral 

Inh. 

inh. 

Inh. 

Oral 

Rad. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Chr. 

Acute 

int. 

Chr. 

Acute 

Int. 

Chr. 

Int. 

Int. 

Chr. 

Int. 

Acute 

Chr. 

0.1 ppm 

0.05 ppm 

0.02 ppm 

0.3 mg/kg/day 

0.1 mg/kg/day 

0.01 mg/kg/day 

0.5 ppm 

0.2 ppm 

0.05 ppm 

0.003 mg/kg/day 

0.003 mg/kg/day 

0.001 mg/kg/day 

0.000005 mg/m3 

0.001 mg/m3 

0.0001 mg/m3 

0.01 mg/kg/day 

4 mSv 

1 mSv/yr 

30 

100 

100 

100 

100 

1000 

100 

300 

1000 

10 

10 

100 

100 

30 

10 

100 

3 

3 

100 Develop. 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Neurol. 

Hepatic 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Resp. 

Resp. 

Resp. 

Hemato. 

Develop. 

Other 

Gastro 

Int. 

Resp. 

Neurol. 

Neurol. 

Repro. 

Neurol. 

Hepatic 

Neurol. 

Repro. 

Develop. 

Hepatic 

100 

100 

100 

100 

1000 

1000 

100 

300 

1000 

100 

300 Develop. 

100 

100 

Repro. 

Repro. 

100 Develop. 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
P.34 

ATSD R - Minimal Risk Levels for Hazardous Substances (MRLs) 

DI-N-OCTYL PHTHALATE 

DIAZINON 

DICHLORVOS 

DIELDRIN 

DIETHYL PHTHALATE 

DIISOPROPYL METHYLPHOSPHONATE 

(DIMP) 

DISULFOTON 

ENDOSULFAN 

ENDRIN 

ETHION 

ETHYLBENZENE 

ETHYLENE GLYCOL 

ETHYLENE OXIDE 

FLUORANTHENE 

FLUORENE 

FLUORIDE, SODIUM 

FLUORINE 

FORMALDEHYDE 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Oral 

Oral 

Oral 

Inh. 

Oral 

Oral 

Oral 

Oral 

inh. 

Inh. 

Oral 

Inh. 

Oral 

Oral 

Oral 

Inh. 

Inh. 

Oral 

Acute 

Int. 

Int. 

Int. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Chr. 

Int. 

Chr. 

Acute 

Int. 

Int. 

Chr. 

Acute 

Int. 

Acute 

Int. 

Chr. 

Int. 

Chr. 

int. 

Chr. 

Acute 

Int. 

Chr. 

Int. 

Acute 

Acute 

Chr. 

Int. 

Int. 

Int. 

Chr. 

Acute 

Acute 

Int. 

Chr. 

Int. 

Chr. 

3 mg/kg/day 

0.4 mg/kg/day 

0.009 mg/m3 

0.0002 mg/kg/day 

0.002 ppm 

0.0003 ppm 

0.00006 ppm 

0.004 mg/kg/day 

0.003 mg/kg/day 

0.0005 mg/kg/day 

0.0001 mg/kg/day 

0.00005 mg/kg/day 

7 mg/kg/day 

6 mg/kg/day 

0.8 mg/kg/day 

0.6 mg/kg/day 

0.006 mg/m3 

0.0002 mg/m3 

0.001 mg/kg/day 

0.00009 mg/kg/day 

0.00006 mg/kg/day 

0.005 mg/kg/day 

0.002 mg/kg/day 

0.002 mg/kg/day 

0.0003 mg/kg/day 

0.002 mg/kg/day 

0.002 mg/kg/day 

0.0004 mg/kg/day 

1.0 ppm 

0.5 ppm 

2.0 mg/kg/day 

2.0 mg/kg/day 

0.09 ppm 

0.4 mg/kg/day 

0.4 mg/kg/day 

0.06 mg/kg/day 

0.01 ppm 

0.04 ppm 

0.03 ppm 

0.008 ppm 

0.3 mg/kg/day 

0.2 mg/kg/day 

300 

100 

30 

100 

100 

100 

100 

1000 

10 

100 

100 

100 

300 

300 

100 

100 

30 

30 

100 

100 

1000 

100 

100 

100 

100 

30 

30 

150 

100 

100 

100 

100 

100 

300 

300 

10 

10 

9 

30 

30 

100 

100 

Page 6 of 11 

Hepatic 

Hepatic 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Hepatic 

Repro. 

Hepatic 

Hemato. 

Hemato. 

Neurol. 

Neurol. 

Neurol. 

Develop. 

Neurol. 

Xmxmino. 

Hepatic 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Neurol. 

Develop. 

Renal 

Develop. 

Renal 

Renal 

Hepatic 

Hepatic 

Musculo. 

Resp. 

Resp. 

Resp. 

Resp. 

Gastro. 

Gastro. 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
P.35 

ATSDR - Minimal Risk Levels for Hazardous Substances (MRLs) Page 7 of 11 

FUEL OIL NO. 2 

HEXACHLOROBENZENE 

HEXACHLOROBUTADIENE 

HEXACHLOROCYCLOHEXANE, ALPHAHEXACHLOROCYCLOKEXANE, BETAKEXACHLOROCYCLOPENTADIENE 

HEXACHLOROCYCLOHEXANE, GAMMAHEXACHLOROETHANE 

HEXAMETHYLENE DIISOCYANATE 

HEXANE, NHYDRAZINE 

HYDROGEN FLUORIDE 

HYDROGEN SULFIDE 

IODIDE 

IONIZING RADIATION, N.O.S. 

ISOPHORONE 

JP-4 

JP-5/JP-8 

JP-7 

KEROSENE 

MALATHION 

Inh. 

Oral 

Oral 

Oral 

Oral 

Inh. 

Oral 

Oral 

Inh. 

Oral 

Inh. 

Inh. 

Inh. 

Inh. 

Inh. 

Oral 

Rad. 

Oral 

Inh. 

Inh. 

Inh. 

Inh. 

Inh. 

Oral 

Acute 

Acute 

Int. 

Chr. 

Int. 

Chr. 

Acute 

Int. 

Int. 

Chr. 

Int. 

Acute 

Int. 

Acute 

Int. 

Acute 

Int. 

Int. 

Chr. 

Chr. 

Int. 

Acute 

Int. 

Acute 

Int. 

Acute 

Chr. 

Acute 

Chr. 

Int. 

Chr. 

Int. 

Int. 

Chr. 

Int. 

Acute 

Int. 

Int. 

Chr. 

0.02 mg/m3 

0.008 mg/kg/day 

0.0001 mg/kg/day 

0.00005 mg/kg/day 

0.0002 mg/kg/day 

0.008 mg/kg/day 

0.2 mg/kg/day 

0.0006 mg/kg/day 

0.01 ppm 

0.0002 ppm 

0.1 mg/kg/day 

0.01 mg/kg/day 

0.00001 mg/kg/day 

6 ppm 

6 ppm 

1 mg/kg/day 

0.01 mg/kg/day 

0.00003 ppm 

0.00001 ppm 

0.6 ppm 

0.004 ppm 

0.03 ppm 

0.02 ppm 

0.07 ppm 

0.03 ppm 

0.01 mg/kg/day 

0.01 mg/kg/day 

4 mSv 

1 mSv/yr 

3 mg/kg/day 

0.2 mg/kg/day 

9 mg/m3 

3 mg/m3 

0.3 mg/m3 

0.01 mg/m3 

0.2 mg/m3 

0.02 mg/m3 

0.02 mg/kg/day 

0.02 mg/kg/day 

1000 

300 

90 

300 

1000 

100 

100 

300 

30 

90 

100 

100 

1000 

30 

30 

100 

100 

30 

90 

100 

300 

30 

30 

30 

30 

1 

1 

3 

3 

100 

1000 

300 

300 

300 

1000 

100 

1000 

10 

100 

Neurol. 

Develop 

Repro. 

Develop 

Renal 

Hepatic 

Neurol. 

Hepatic 

Resp. 

Resp. 

Renal 

Neurol. 

Xmmuno. 

Neurol. 

Neurol. 

Hepatic 

Hepatic 

Resp. 

Resp. 

Neurol. 

Hepatic 

Resp. 

Resp. 

Resp. 

Resp. 

Endocr. 

Endocr. 

Neurol. 

Other 

Other 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Neurol. 

Resp. 

Neurol. 

Neurol. 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
ATSDR - Minimal Risk Levels for Hazardous Substances (MRLs) Page 8 of 11 

MANGANESE 

MERCURIC CHLORIDE 

MERCURY 

METHOXYCHLOR 

METHYL PARATHION 

METHYL-T-BUTYL ETHER 

METHYLENE CHLORIDE 

METHYLMERCURY 

MIREX 

MUSTARD GAS 

N-NITROSODI-N-PROPYLAMINE 

NAPHTHALENE 

NICKEL 

PENTACHLOROPHENOL 

PHOSPHORUS, WHITE 

POLYBROMINATED BIPHENYLS (PBBs) 

POLYBROHINATED DIPHENYL ETHERS 

POLYCHLORINATED BIPHENYLS (PCBs) 

Aroclor 1254 

PROPYLENE GLYCOL DINITRATE 

Inh. 

Oral 

Inh. 

Oral 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Oral 

Oral 

Inh. 

Oral 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Oral 

Oral 

Oral 

Inh. 

Chr. 

Acute 

Int. 

Chr. 

Int. 

Int. 

Chr. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Acute 

Int. 

Chr. 

Acute 

Chr. 

Chr. 

Chr. 

Acute 

Acute 

Int. 

Acute 

Chr. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Acute 

Acute 

int. 

Int. 

Chr. 

Acute 

Int. 

Chr. 

0.00004 mg/m3 

0.007 mg/kg/day 

0.002 mg/kg/day 

0.0002 mg/m3 

0.005 mg/kg/day 

0.0007 mg/kg/day 

0.0003 mg/kg/day 

2 ppm 

0.7 ppm 

0.7 ppm 

0.4 mg/kg/day 

0.3 mg/kg/day 

0.6 ppm 

0.3 ppm 

0.3 ppm 

0.2 mg/kg/day 

0.06 mg/kg/day 

0.0003 mg/kg/day 

0.0008 mg/kg/day 

0.0002 mg/m3 

0.5 ug/kg/day 

0.02 ug/kg/day 

0.095 mg/kg/day 

0.002 ppm 

0.05 mg/kg/day 

0.02 mg/kg/day 

0.0002 mg/m3 

0.005 mg/kg/day 

0.001 mg/kg/day 

0.001 mg/kg/day 

0.02 mg/m3 

0.0002 mg/kg/day 

0.01 mg/kg/day 

0.03 mg/kg/day 

0.007 mg/kg/day 

0.03 ug/kg/day 

0.02 ug/kg/day 

0.003 ppm 

0.00004 ppm 

0.00004 ppm 

500 

100 

100 

30 

1000 

300 

100 

100 

100 

100 

100 

300 

100 

90 

30 

100 

100 

4 

100 

900 

1000 

1000 

100 

1000 

1000 

300 

30 

1000 

1000 

1000 

30 

100 

100 

30 

300 

300 

300 

10 

1000 

1000 

Neurol. 

Renal 

Renal 

Neurol. 

Repro. 

Neurol. 

Hemato. 

Neurol. 

Neurol. 

Renal 

Neurol. 

Hepatic 

Neurol. 

Hepatic 

Hepatic 

Neurol. 

Hepatic 

Develop 

Hepatic 

Resp. 

Develop 

Gastro. 

Hepatic 

Resp. 

Neurol. 

Hepatic 

Resp. 

Develop 

Repro. 

Endocr. 

Resp. 

Repro. 

Endocr. 

Endocr. 

Hepatic 

Neurol. 

Immuno. 

Neurol. 

Hemato. 

Hemato. 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
PROPYLENE GLYCOL 

REFRACTORY CERAMIC FIBERS 

SELENIUM 

STRONTIUM 

STYRENE 

SULFUR DIOXIDE 

TETRACHLOROETHYLENE 

TITANIUM TETRACHLORIDE 

TOLUENE 

TOXAPHENE 

TRICHLOROETHYLENE 

URANIUM, HIGHLY SOLUBLE SALTS 

URANIUM, INSOLUBLE COMPOUNDS 

VANADIUM 

VINYL ACETATE 

VINYL CHLORIDE 

XYLENE, MXYLENE, PXYLENES, TOTAL 

ZINC 

1 -METHYLNAPHTHALENE 

http://www.atsdr.cdc.gov/mrls.html 

us Sub 

Inh. 

Inh. 

Oral 

Oral 

Inh. 

Oral 

Inh. 

Inh. 

Oral 

Inh. 

Inh. 

Oral 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Inh. 

Inh. 

Oral 

Inh. 

Inh. 

Oral 

Oral 

Oral 

Inh. 

Oral 

Oral 

Oral 

stances ( 

Int. 

Chr. 

Chr. 

Int. 

Chr. 

Int. 

Acute 

Acute 

Chr. 

Acute 

Int. 

Chr. 

Acute 

Chr. 

Acute 

int. 

Acute 

int. 

Acute 

Int. 

Acute 

Int. 

Chr. 

Int. 

Int. 

Acute 

Int. 

Int. 

Acute 

Int. 

Chr. 

Int. 

Acute 

Acute 

Int. 

Chr. 

int. 

Int. 

Chr. 

Chr. 

MRLs) 

0.009 ppm 

0.03 fibers/cc 

0.005 mg/kg/day 

2 mg/kg/day 

0.06 ppm 

0.2 mg/kg/day 

0.01 ppm 

0.2 ppm 

0.04 ppm 

0.05 mg/kg/day 

0.01 mg/m3 

0.0001 mg/m3 

1 ppm 

0.08 ppm 

0.8 mg/kg/day 

0.02 mg/kg/day 

0.005 mg/kg/day 

0.001 mg/kg/day 

2 ppm 

0.1 ppm 

0.2 mg/kg/day 

0.0004 mg/m3 

0.0003 mg/m3 

0.002 mg/kg/day 

0.008 mg/m3 

0.0002 mg/m3 

0.003 mg/kg/day 

0.01 ppm 

0.5 ppm 

0.03 ppm 

0.00002 mg/kg/day 

0.6 mg/kg/day 

1 mg/kg/day 

1 ppm 

0.7 ppm 

0.1 ppm 

0.2 mg/kg/day 

0.3 mg/kg/day 

0.3 mg/kg/day 

0.07 mg/kg/day 

Page 9 of 11 

1000 Resp. 

30 Resp. 

3 Dermal 

30 Musculo. 

100 Neurol. 

1000 Hepatic 

9 Resp. 

10 Neurol. 

100 Neurol. 

100 Develop. 

90 Resp. 

90 Resp. 

10 Neurol. 

100 Neurol. 

300 Neurol. 

300 Neurol.__ 

1000 Hepatic 

300 Hepatic 

30 Neurol. 

300 Neurol. 

300 Develop. 

90 Renal 

30 Renal 

30 Renal 

30 Renal 

100 Resp. 

100 Renal 

100 Resp. 

100 Develop. 

300 Hepatic 

1000 Hepatic 

1000 Hepatic 

100 Neurol. 

100 Neurol. 

300 Develop. 

100 Neurol. 

1000 Renal 

3 Hemato. 

3 Hemato. 

1000 Resp. 

7/10/2003 
P.38 

ATSDR - Minimal Risk Levels for Hazardous Substances (MRLs) 

1,l-DICHLOROETHENE 

1,1-DIMETHYLHYDRAZINE 

1,1,1-TRICHLOROETHANE 

1,1,2-TRICHLOROETHANE 

1,1,2,2-TETRACHLOROETHANE 

1,2-DIBROMO-3-CHLOROPROPANE 

1,2-DICHLOROETHENE, CIS1,2-DICHLOROETHANE 

1,2-DICHLOROPROPANE 

Page 10 of 11 1 

1,2-DICHLOROETHENE, TRANS -

1,2-DIMETHYLHYDRAZINE 

1,2,3-TRICKLOROPROPANE 

1,3-DICHLOROPROPENE 

1, 3-DINITROBENZENE 

1,4-DICHLOROBENZENE 

2-BUTOXYETHANOL 

2,3,4,7,8-PENTACHLORODIBENZOFURAN 

Inh. 

Oral 

Inh. 

Inh. 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Oral 

Inh. 

Oral 

Inh. 

Oral 

inh. 

Oral 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Inh. 

Oral 

Oral 

int. 

Chr. 

Int. 

Acute 

Int. 

Acute 

Int. 

Int. 

Int. 

Chr. 

int. 

Int. 

Acute 

Int. 

Chr. 

Int. 

Acute 

Int. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Int. 

Int. 

Acute 

Int. 

Int. 

Chr. 

Acute 

Int. 

Acute 

Int. 

Chr. 

Int. 

Acute 

Int. 

Chr. 

Acute 

Int. 

Acute 

Int. 

0.02 ppm 

0.009 mg/kg/day 

0.0002 ppm 

2 ppm 

0.7 ppm 

0.3 mg/kg/day 

0.04 mg/kg/day 

0.4 ppm 

0.6 mg/kg/day 

0.04 mg/kg/day 

0.0002 ppm 

0.002 mg/kg/day 

1 mg/kg/day 

0.3 mg/kg/day 

0.6 ppm 

0.2 mg/kg/day 

0.05 ppm 

0.007 ppm 

0.1 mg/kg/day 

0.07 mg/kg/day 

0.09 mg/kg/day 

0.2 ppm 

0.2 ppm 

0.2 mg/kg/day 

0.0008 mg/kg/day 

0.0003 ppm 

0.06 mg/kg/day 

0.003 ppm 

0.002 ppm 

0.008 mg/kg/day 

0.0005 mg/kg/day 

0.8 ppm 

0.2 ppm 

0.1 ppm 

0.4 mg/kg/day 

6 ppm 

3 ppm 

0.2 ppm 

0.4 mg/kg/day 

0.07 mg/kg/day 

0.001 ug/kg/day 

0.00003 ug/kg/day 

100 

1000 

300 

100 

100 

100 

100 

300 

100 

1000 

100 

1000 

100 

100 

90 

300 

1000 

1000 

1000 

1000 

1000 

1000 

1000 

100 

1000 

100 

100 

100 

100 

100 

1000 

100 

100 

100 

300 

9 

9 

3 

90 

1000 

3000 

3000 

Hepatic 

Hepatic 

Hepatic 

Neurol. 

Neurol. 

Neurol. 

Hepatic 

Hepatic 

Body Wt. 

Resp. 

Repro. 

Repro. 

Hemato. 

Hemato. 

Hepatic 

Renal 

Resp. 

Resp. 

Neurol. 

Hemato. 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Hepatic 

Resp. 

Hepatic 

Resp. 

Resp. 

Repro. 

Hemato. 

Develop 

Hepatic 

Hepatic 

Hepatic 

Hemato. 

Hemato. 

Hemato. 

Hemato. 

Hepatic 

Immune 

Hepatic 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003 
^TSDR - Minimal Risk Levels for Hazardous Substances (MRLs) Page11 of 11 

2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN Oral 

2,4-DICHLOROPKENOL 

2,4-DINITROPHENOL 

2,4-DINITROTOLUENE 

2,4,6-TRINITROTOLUENE 

2,6-DINITROTOLUENE 

4-CHLOROPHENOL 

Oral 

Oral 

Oral 

Oral 

Oral 

Oral 

4,4'-METHYLENEBIS(2-CHLOROANILINE) Oral 

4,4'-METHYLENEDIANILINE Oral 

4, 6-DINITRO-O-CRESOL Oral 

Acute 0.0002 ug/kg/day 

Int. 0.00002 ug/kg/day 

Chr. 0.000001 ug/kg/day 

Int. 0.003 mg/kg/day 

Acute 0.01 mg/kg/day 

Acute 0.05 mg/kg/day 

Chr. 0.002 mg/kg/day 

Int. 0.0005 mg/kg/day 

Int. 0.004 mg/kg/day 

Acute 0.01 mg/kg/day 

Chr. 0.003 mg/kg/day 

Acute 0.2 mg/kg/day 

Int. 0.08 mg/kg/day 

Acute 0.004 mg/kg/day 

Int. 0.004 mg/kg/day 

21 Timmmo. 

30 Lymphor. 

90 Develop. 

100 Hmnuno. 

100 Body Wt. 

100 Neurol. 

100 Hemato. 

1000 Hepatic 

1000 Hemato. 

100 Hepatic 

3000 Hepatic 

300 Hepatic 

100 Hepatic 

100 Neurol. 

100 Neurol. 

Total number of MRLs: 315 

This document last updated on January 23, 2003 

Dr. Selene Chou / CJC3@cdc.gov 

ATSDR Home | Search | Index | Glossary | Contact Us 

About ATSDR | News Archive | ToxFAQs | HazDat | Public Health Assasstnants 

Privacy Policy | External Links Disclaimer | Accessibility 

U.S. Department ot Health and Human Services 

http://www.atsdr.cdc.gov/mrls.html 7/10/2003