Tetraethyl lead (CASRN 78-00-2)
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0109
Tetraethyl lead;
CASRN 78-00-2
Health assessment information on a chemical substance is included in IRIS
only after a comprehensive review of chronic toxicity data by U.S. EPA
health scientists from several Program Offices and the Office of Research
and Development. The summaries presented in Sections I and II represent
a consensus reached in the review process. Background information and
explanations of the methods used to derive the values given in IRIS are
provided in the Background Documents.
STATUS OF DATA FOR Tetraethyl lead
File First On-Line 01/31/1987
Category (section) |
Status |
Last Revised |
---|---|---|
Oral RfD Assessment (I.A.) | on-line | 03/01/1988 |
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 — Tetraethyl lead
CASRN — 78-00-2
Last Revised — 03/01/1988
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* |
UF |
MF |
RfD |
---|---|---|---|---|
Histopathology of Rat Subchronic Schepers, 1964 |
NOAEL: none LOAEL: 1.7 ug/kg/day |
10,000
|
1
|
1E-7
mg/kg/day |
*Conversion Factors: 5 days/7 days; thus, 1.7 ug/kg/day x 5 days/7 days = 1.2 ug/kg/day
__I.A.2. Principal and Supporting Studies (Oral RfD)
Schepers, G.W. 1964. Tetraethyl and tetramethyl lead. Arch. Environ.
Health. 8: 277-295.
In a 20-week study, Schepers (1964) administered tetraethyl lead in peanut oil
by gavage to groups of 12 CD rats (6/sex) at 1.7 and 170 ug/kg/bw 5 days/week.
Gross observations revealed swollen livers and fatty plaques in the thymus at
both dose groups. Histologic preparations revealed hepatocyte vacuolization,
cytoplasmic degeneration and neuronal damage among low-dose rats. Rats
exposed to the higher dose developed similar, but more severe,
histopathologies. Based on these findings, a LOAEL of 1.2 ug/kg/day (1.7
ug/kg/day x 5 days/7 days) was determined.
A subchronic inhalation study by Davis et al. (1963) in rats and dogs supports
these findings. However, the equivalent oral doses derived from this study
are substantially higher than the LOAEL derived from the Schepers (1964)
study. Therefore, a human RfD of 0.0001 ug/kg/day was derived based on the
LOAEL of 1.2 ug/kg/day from Schepers (1964) and on a standard scaling factor
of 10,000.
__I.A.3. Uncertainty and Modifying Factors (Oral RfD)
UF — The uncertainty factor of 10,000 represents 10 to extrapolate from
animal to human, 10 to convert subchronic to chronic exposure, and 10 to
protect for sensitive humans, and an additional factor of 10 to convert a
LOAEL to a NOAEL.
MF — None
__I.A.4. Additional Studies/Comments (Oral RfD)
The database contained limited long-term oral studies, as well as limited subchronic inhalation and oral data. Reproductive, carcinogenicity, and teratogenicity data are available, but are inconclusive. Limited epidemiologic data are also available.
__I.A.5. Confidence in the Oral RfD
Study — Medium
Database — Medium
RfD — Medium
The chosen study is given medium to low confidence because, although only a few animals/sex/dose were tested, a good histopathologic exam was conducted and a dose-severity was observed. The database was considered to have medium to low confidence because some supporting information was available. Confidence in the RfD can also be considered medium to low.
__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 — None
Agency Work Group Review — 08/05/1985
Verification Date — 08/05/1985
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 Tetraethyl lead conducted in September 2002 identified one or more significant new studies. IRIS users may request the references for those studies from 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).
_I.B. Reference Concentration for Chronic Inhalation Exposure (RfC)
Substance Name — Tetraethyl lead
CASRN — 78-00-2
Not available at this time.
_II. Carcinogenicity Assessment for Lifetime Exposure
Substance Name — Tetraethyl lead
CASRN — 78-00-2
This substance/agent has not undergone a complete evaluation and determination under US EPA's IRIS program for evidence of human carcinogenic potential.
_VI. Bibliography
Substance Name — Tetraethyl lead
CASRN — 78-00-2
Last Revised — 01/01/1990
_VI.A. Oral RfD References
Davis, R.K., A.W. Horton, E.E. Larson and K.L. Stemmer. 1963. Inhalation of
tetramethyllead and tetraethyllead. Arch. Environ. Health. 6: 473-479.
Schepers, G.W. 1964. Tetraethyl and tetramethyl lead. Arch. Environ.
Health. 8: 277-295.
_VI.B. Inhalation RfC References
None
_VI.C. Carcinogenicity Assessment References
None
_VII. Revision History
Substance Name — Tetraethyl lead
CASRN — 78-00-2
Date |
Section |
Description |
---|---|---|
04/10/1987 | I.A.1. | RfD exponent corrected |
01/01/1990 | VI. | Bibliography on-line |
01/01/1992 | I.A.7. | Primary contact changed |
01/01/1992 | IV. | Regulatory actions updated |
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. |
_VIII. Synonyms
Substance Name — Tetraethyl lead
CASRN — 78-00-2
Last Revised — 01/31/1987
- 78-00-2
- Lead, Tetraethyl-
- NCI-C54988
- Plumbane, Tetraethyl-
- TEL
- Tetraethyl Lead
- Tetraethylplumbane