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Abstract for IMM98003

Dichloroacetic Acid

CASRN: 79-43-6
Chemical Formula: C2H2Cl2O2
Molecular Weight: 128.942
Report Date: July 2002


The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings have not been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of the NTP or the U.S. Government.

Disinfection by-products (DBPs) are contaminants found in drinking water. DBPs are formed as by-products as a result of the chlorination/ozination process used to purify water to acceptable drinking water standards. The potential effects of drinking water contaminants to affect adversely the immune system is a concern of both the Environmental Protection Agency (EPA) and the National Institute of Environmental Health Sciences (NIEHS). Several drinking water DBPs have been identified and selected for evaluation of their potential effects on the immune system in a joint project between the EPA and the NIEHS.

The National Toxicology Program (NTP) requested that a dose range-finding study be performed in order to establish the potential effects of dichloroacetic acid (DCA) on the immune system and to determine doses that could be used in a full immunotoxicology study. These studies were conducted in female B6C3F1 mice. The animals were exposed to DCA based on the concentration of the test article in the drinking water. Five DCA concentrations of 125, 250, 500, 1000 and 2000 mg/L for 28 days were utilized. The national average for DCA in finished drinking water is 12.4 µg/l. DCA solutions were prepared fresh every two weeks in tap water and stored refrigerated. The in-life phase of these studies was carried out between 10 April 1998 and 26 May 1998.

The baseline toxicology studies are summarized in Table ES-1. There were few notable changes among the standard toxicological parameters that were assessed with the exception of a dose-related increase in liver weight and decreases in reticulocytes counts.

The immunological studies are summarized in Table ES-2. In contrast to the toxicological effects observed, DCA, at the doses administered, had virtually no effect on the various immunological endpoints evaluated.

In summary, based on the results of this range-finding study, further investigation of the effect of DCA on the immune system appears unwarranted. As a disinfection by-product, human exposure to DCA can occur from the drinking water; however, the immune system does not appear to be a major target organ for DCA.


Table ES-1
Summary Table for Toxicology Studies

Body Weight

Parameter Results Maximum
Dose Comment
Day 1 No Effect


Day 8 No Effect


Day 15 No Effect


Day 22 No Effect


Day 29 No Effect


Weight Changes
Parameter Results Maximum
Dose Comment
Day 8-1 No Effect


Day 15-1 No Effect


Day 22-1 No Effect


Day 29-1 No Effect


Parameter Results Maximum
Dose Comment
Gross Pathology No Effect


Histopathology Not Conducted


Organ Weights



Liver Increase 41% 2000 ml/L Abs. Bdy Wgt
% Bdy Wgt
Spleen No Effect


Lungs No Effect


Thymus No Effect


Kidney No Effect


Parameter Results Maximum
Dose Comment
RBCs No Effect


Hemoglobin Decrease 6% 2000 mg/L
Hematocrit Decrease 4% 2000 mg/L
MCV Decrease 3% 2000 mg/L
MCH Decrease 5% 2000 mg/L
MCHC Decrease 2% 125 mg/L
2000 mg/L

Platelets No Effect


Reticulocytes Decrease 25% 1000 mg/kg
Leukocytes No Effect


% Lymphocytes No Effect


% Neutrophils No Effect


% Eosinophils No Effect


Abs Lymphocytes No Effect


Abs Neutrophils Increase 108% 2000 mg/L
Abs Eosinophils No Effect



Table ES-2
Summary Table for Immunology Studies

Surface Makers (Absolute Values)

Parameter Results Maximum
Dose Comment
Ig+ No Effect


CD3+ No Effect


CD4+CD8- No Effect


CD4-CD8+ No Effect


CD4+CD8+ No Effect


NK1.1+CD3- No Effect


Mac-3+ No Effect


IgM Humoral Immune Response to Sheep Erythrocytes
Parameter Results Maximum
Dose Comment
IgM AFC Response No Effect


Serum Titer No Effect


Mixed Leukocyte Response
Parameter Results Maximum
Dose Comment
Responders Only No Effect


Responders + Stimulators No Effect


Parameter Results Maximum
Dose Comment
PEC Activity without MAF No Effect


PEC Activity with MAF No Effect


NK Cell Activity
Parameter Results Maximum
Dose Comment
NK Cell Activity No Effect