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Dalapon, sodium salt (CASRN 75-99-0)

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Dalapon, sodium salt; CASRN 75-99-0

Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data, as outlined in the IRIS assessment development process. Sections I (Health Hazard Assessments for Noncarcinogenic Effects) and II (Carcinogenicity Assessment for Lifetime Exposure) present the conclusions that were reached during the assessment development process. Supporting information and explanations of the methods used to derive the values given in IRIS are provided in the guidance documents located on the IRIS website.

STATUS OF DATA FOR Dalapon, sodium salt

File First On-Line 01/31/1987

Category (section)
Last Revised
Oral RfD Assessment (I.A.) on-line 06/01/1989
Inhalation RfC Assessment (I.B.) no data
Carcinogenicity Assessment (II.) no data

_I.  Chronic Health Hazard Assessments for Noncarcinogenic Effects

_I.A. Reference Dose for Chronic Oral Exposure (RfD)

Substance Name — Dalapon, sodium salt
CASRN — 75-99-0
Last Revised — 06/01/1989

The oral Reference Dose (RfD) is based on the assumption that thresholds exist for certain toxic effects such as cellular necrosis. It is expressed in units of mg/kg-day. In general, the RfD is an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. Please refer to the Background Document for an elaboration of these concepts. RfDs can also be derived for the noncarcinogenic health effects of substances that are also carcinogens. Therefore, it is essential to refer to other sources of information concerning the carcinogenicity of this substance. If the U.S. EPA has evaluated this substance for potential human carcinogenicity, a summary of that evaluation will be contained in Section II of this file.

__I.A.1. Oral RfD Summary

Critical Effect
Experimental Doses*

Increased kidney
body weight ratio

2-Year Rat Study
Oral Exposure (diet)

Paynter et al., 1960

NOEL: 15 mg/kg/day
converted to
8.45 mg/kg/day

LEL: 50 mg/kg/day
converted to
28.17 mg/kg/day


*Conversion Factors: [15 or 50 mg/kg/day x 0.65 mg dalapon- Na/mg of com- mercial product x (143 g dalapon/165 g dalapon-Na)] = 8.45 or 28.17 mg/kg/day, respectively

__I.A.2. Principal and Supporting Studies (Oral RfD)

Paynter, O.E., T.W. Tusing, D.D. McCollister and V.K. Rowe. 1960. Toxicology of Dalapon Sodium (2,2-dichloropropoionic acid, sodium salt). J. Agriculture Food Chemicals. 8: 47-51.

Albino Carworth rats (24 male, 24 female/group) were fed diets providing 0, 5, 15, or 50 mg commerial dalapon sodium salt/kg bw/day for 2 years. Hematological parameters were examined at timed intervals and histopathology was performed at 104 weeks. A statistically significant (p<0.05) increase over controls was observed in the kidney-to-body weight ratios of male rats receiving 50 mg/kg/day. No differences from controls were observed. Kidney lesions were not observed.

Paynter et al. (1960) reported that the commercial-grade dalapon sodium contained 65% of the pure sodium salt of dalapon. The dose is further adjusted to pure dalapon by multiplying by the ratio of the molecular weight of dalapon (143) to its sodium salt (165).

__I.A.3. Uncertainty and Modifying Factors (Oral RfD)

UF — An uncertainty factor of 100 was used to account for the inter- and intraspecies differences. An additional UF of 3 was used to account for the incomplete database on chronic toxicity.

MF — None

__I.A.4. Additional Studies/Comments (Oral RfD)

Although the database for Dalapon was judged not to be acceptable for OPP's regulatory requirements by current standards, the existing database does provide useful information to derive an RfD.

Data Considered for Establishing the RfD

1) 2-Year Feeding - rat: Principal study - see previous description; no core grade (Paynter et al., 1960)

2) Teratology - rat: Maternal Toxicity NOEL=none; Maternal Toxicity LEL=500 mg/kg/day (LDT; decreased weight gain in all doses); Fetal Toxicity NOEL=none; Fetal Toxicity LEL=500 mg/kg/day (LDT; decreased and delayed ossification of sternebrae hyoids and sacral arches at all doses); No teratogenic reponses; core grade supplementary (Dow Chemical, 1971)

3) 2-Year Feeding - dog: The Paynter et al. (1960) study is not considered reliable.

4) Multi-generation Reproduction - rat: The Paynter et al. (1960) study is not considered reliable.

Data Gap(s): Chronic Rat Feeding Study, Chronic Dog Feeding Study, Rat Reproduction Study, Rat Teratology Study, Rabbit Teratology Study

__I.A.5. Confidence in the Oral RfD

Study — Low
Database — Low
RfD — Low

The critical study is given a low confidence rating for the following reasons: 1) Hematology was performed on only 3 males and 3 females, 2) clinical chemistry was not performed, 3) histology was performed on only half of the survivers at each dose, and 4) only a limited number of tissues were examined. Since there are extensive data gaps existing for dalapon, the data base is given a low confidence rating. Low confidence in the RfD follows.

__I.A.6. EPA Documentation and Review of the Oral RfD

Source Document — This assessment is not presented in any existing U.S. EPA document.

Other EPA Documentation — Pesticide Registration Standard, January 1987; Pesticide Registration Files

Agency Work Group Review — 10/09/1985, 07/22/1986, 07/15/1987, 08/12/1987, 06/22/1988

Verification Date — 06/22/1988

Screening-Level Literature Review Findings — A screening-level review conducted by an EPA contractor of the more recent toxicology literature pertinent to the RfD for Dalapon, sodium salt, conducted in September 2002 did not identify any critical new studies. IRIS users who know of important new studies may provide that information to the IRIS Hotline at hotline.iris@epa.gov or (202)566-1676.

__I.A.7. EPA Contacts (Oral RfD)

Please contact the IRIS Hotline for all questions concerning this assessment or IRIS, in general, at (202)566-1676 (phone), (202)566-1749 (FAX) or hotline.iris@epa.gov (internet address).

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_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)

Substance Name — Dalapon, sodium salt
CASRN — 75-99-0

Not available at this time.

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_II.  Carcinogenicity Assessment for Lifetime Exposure

Substance Name — Dalapon, sodium salt
CASRN — 75-99-0

This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.

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_III.  [reserved]
_IV.  [reserved]
_V.  [reserved]

_VI.  Bibliography

Substance Name — Dalapon, sodium salt
CASRN — 75-99-0
Last Revised — 02/01/1993

_VI.A. Oral RfD References

Dow Chemical Company. 1971. MRID No. 00082692. Available from EPA. Write to FOI, EPA, Washington, DC 20460.

Paynter, O.E., T.W. Tusing, D.D. McCollister and V.K. Rowe. 1960. Toxicology of Dalapon Sodium (2,2-dichloropropoionic acid, sodium salt). J. Agriculture Food Chemicals. 8: 47-51.

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_VI.B. Inhalation RfC References


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_VI.C. Carcinogenicity Assessment References


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_VII.  Revision History

Substance Name — Dalapon, sodium salt
CASRN — 75-99-0

09/30/1987 All CASRN changed
08/22/1988 I.A. Oral RfD summary replaced - RfD changed
12/01/1988 I.A.4. Study description deleted
06/01/1989 I.A.6. Work group review date added
01/01/1990 VI. Bibliography on-line
01/01/1992 IV. Regulatory actions updated
02/01/1993 III.A. Health Advisory on-line
02/01/1993 VI.D. Health Advisory references on-line
08/01/1995 I.A.6 EPA's RfD/RfC and CRAVE workgroups were discontinued in May, 1995. Chemical substance reviews that were not completed by September 1995 were taken out of IRIS review. The IRIS Pilot Program replaced the workgroup functions beginning in September, 1995.
04/01/1997 III., IV., V. Drinking Water Health Advisories, EPA Regulatory Actions, and Supplementary Data were removed from IRIS on or before April 1997. IRIS users were directed to the appropriate EPA Program Offices for this information.
12/03/2002 I.A.6. Screening-Level Literature Review Findings message has been added.

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_VIII.  Synonyms

Substance Name — Dalapon, sodium salt
CASRN — 75-99-0
Last Revised — 01/31/1987

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