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Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Study period:
no data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The study was performed according to a method equivalent to OECD 417. No data on GLP. The publication describes the findings in detail.

Data source

Reference
Reference Type:
publication
Title:
[14C]bis(2-chloroethoxy)methane: Comparative absorption, distribution, metabolism and excretion in rats and mice.
Author:
Black, S.R., Decosta, K.S., Patel, P.R., Mathews, J.M.
Year:
2007
Bibliographic source:
Xenobiotica, April 2007; 37(4): 427-440

Materials and methods

Objective of study:
toxicokinetics
Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 417 (Toxicokinetics)
GLP compliance:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Nonradiolabeled BCM
Supplier: Pfaltz and Bauer (Waterbury, CT, USA)
Identity was confirmed by 'H-NMR and GC/MS analysis.

[14]BCM
Supplier: Wizard Laboratories (West Sacramento, CA, USA).
Uniformly radiolabeled in the ethyl groups, with a specific activity of 60.49 mCi/mmol (345.7 µCi/mg).
Radiochemical purity was confirmed by high performance liquid chromatography (HPLC) to be 294% using an isocratic system consisting of a Du Pont Zorbax Rx-C18 column (4.6 x 250mm, 5 pm, Mac-Mod 2 Analytical, Chadds Ford, PA, USA) and a mobile phase of acetonitrile:water (40:60, v:v)with a flow rate of 1 ml/min.
Radiolabelling:
yes
Remarks:
[14C]bis(2-chloroethoxy)methane

Test animals

Species:
other: rats and mice
Strain:
other: F344 and B6C3F1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: from Charles River Laboratories, Inc. (Raleigh, NC, USA)
- Age at study initiation: adult
- Weight at study initiation: rats 239-250g, mice 18-25 g
- Fasting period before study: no data
- Housing: individual glass metabolism cages post dosing
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): Certified Purina Rodent Chow #5002, ad libitum
- Water (e.g. ad libitum): tap water, ad libitum
- Acclimation period: no data

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20.5-23.9
- Humidity (%): 35-65
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: no data

Administration / exposure

Route of administration:
other: IV, oral or dermal
Vehicle:
other: saline, water or ethanol
Details on exposure:
IV
Male rats and male and female mice (n = 3-4) were dosed intravenously via the tail vein with [14C] BCM formulated in saline (1 mg/kg, 5-7 µCi, 1-2 ml/kg).

DERMAL
TEST SITE
- Area of exposure: intrascapular region
- % coverage: 4cm2 rats, 1cm2 mice.
- Type of wrap if used: Non-occlusive foam appliances fixed in place with Hollister's Medical Adhesive were used to prevent access to the dose site by rats; a metal tissue capsule fixed in place with cyanoacrylate adhesive, was used to prevent access by mice.
- Time intervals for shavings or clipplings: the exposure area was clipped the day prior to exposure.

REMOVAL OF TEST SUBSTANCE
- Washing (if done): The dose sites and appliances were washed with a series of soapy water-wetted (ca. 30ml of Liquid Ivory per liter) gauzes followed by water-wetted gauzes.
- Time after start of exposure: 6 hours

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 15-20µL for mice and 50µL for rats
- concentration (if solution): [14]BCM 0.1 and 10mg/kg, 0.3-12.6 µCi

VEHICLE
- Justification for use and choice of vehicle (if other than water): no data
- Amount(s) applied (volume or weight with unit): 15-20µL for mice and 50µL for rats
- Concentration (if solution): no data
- Lot/batch no. (if required): no data
- Purity:

USE OF RESTRAINERS FOR PREVENTING INGESTION: yes

ORAL
PREPARATION OF DOSING SOLUTIONS: formulated in water

VEHICLE
- Justification for use and choice of vehicle (if other than water): water
- Concentration in vehicle: 0.1 and 10 mg/kg, 0.7-9 µCi
- Amount of vehicle (if gavage): 5 ml/kg
- Lot/batch no. (if required): -
- Purity: -

HOMOGENEITY AND STABILITY OF TEST MATERIAL: no data
Duration and frequency of treatment / exposure:
Single doses
Doses / concentrations
Remarks:
Doses / Concentrations:
see details on exposure
No. of animals per sex per dose:
IV n =3-4
oral n=4
dermal n=4
Control animals:
no
Positive control:
Not applicable
Details on study design:
- Dose selection rationale: no data
- Rationale for animal assignment (if not random): no data
Details on dosing and sampling:
PHARMACOKINETIC STUDY (Absorption, distribution, excretion)
- Tissues and body fluids sampled : urine, faeces, blood, plasma, serum or other tissues, cage washes
- Time and frequency of sampling:
Urine and feces were collected separately up to 72 h post dosing into round-bottom flasks cooled with dry ice and were stored in the dark at -20°C until analyzed. Radiolabeled components in breath and/or volatized from skin were collected continuously for 72 h post dosing. Air from the metabolism cage (flow = 200-500 mllmin) passed first through two cryogenic traps containing 60 ml ethanol each and held at 4-C and -60°C, respectively, and then passed through two CO2 traps containing 500 ml 1 N NaOH each. At the end of each experiment, blood was withdrawn from anesthetized (as described above) animals into a heparinized syringe by cardiac puncture. Rats were euthanized by bilateral thoracotomy and mice by cervical dislocation while under anesthesia. Tissues were collected and analyzed for radioactivity to determine tissue distribution following i.v. administration. Carcasses and dermal dose site skin sections were digested in 2 N ethanolic sodium hydroxide. Scintillation cocktail was added to vials containing sections of the protective foam appliances and gauzes used to wash the skin. Metal tissue capsules used on mouse dermal studies were rinsed with acetone and aliquots of the rinsates were added to vials containing scintillation cocktail.

METABOLITE CHARACTERISATION STUDIES
- Tissues and body fluids sampled: urine, faeces, blood, plasma, serum or other tissues, cage washes
- Time and frequency of sampling: see above
- From how many animals: all animals, not pooled
- Method type(s) for identification: Alls samples = liquid scintillation spectrometry (LSS), Urinary metabolite profling and isolation = HPLC.
- Limits of detection and quantification: no data
Statistics:
Means and standard deviations were calculated for the disposition of BCM. Values for test groups were compared by ANOVA followed by Dunnett's test.

Results and discussion

Preliminary studies:
No data

Toxicokinetic / pharmacokinetic studies

Details on absorption:
Absorption of BCM by male rats
Comparison of data obtained following intravenous vs. oral administration to male rats over a range of doses provided an estimate of the degree to which BCM-derived radioactivity was absorbed from the gastrointestinal tract.

I.v. and oral administration of BCM at lower and higher, but presumably non-toxic, doses (Table I) indicated that doses in this range were nearly completely absorbed from the gastrointestinal tract and rapidly excreted.

Absorption of BCM by male and female mice
Studies similar to those described above for rats conducted with both sexes of mice provided
an examination of the effects of both sex and species on the fate of BCM (Table II). A comparison of data in Tables I and II, describing the fate of similar doses of BCM following i.v. or oral gavage to male rats or male and female mice, indicates only minimal sex- or species-related differences in the fate of BCM.

Absorption of BCM by rats and mice following dermal administration
Studies of absorption of BCM by male rats and mice following administration of doses of
0.1 or 10 mg/kg to a protected area of skin indicated that, whereas volatilization and absorption onto the protective devices accounted for most of the dose, dermal absorption was significant. Further, absorption was not significantly altered by dose level in rats (Table III). Rats absorbed approximately 15% of each dose and as observed with oral and i.v. administration. Mice absorbed approximately 18% of the 10mg/kg dose.
Details on distribution in tissues:
Tissue distribution in rats following i. v. administration
Male rats were euthanized at 0.25, 0.5, 1, 2, 4, and 8 h following i.v. administration of 1 mg/kg BCM, and selected tissues were collected for analysis of total radioactivity (Table IV).

*It is noted that scission of the ether linkage changes the specific activity of the resulting fragments. Therefore, the ng-equivalents/g tissue values were calculated assuming 4 labeled carbons. Equivalents representing fragments containing 1 or 2 carbon-14 per mole are underestimated by these ratios.

As anticipated from the rapid removal of radioactivity from blood CM-derived radioactivity was rapidly distributed to the tissues. Of the approximately 80% of the total dose recovered in the tissues assayed at 0.25 h post dosing, only about 2% was in blood. The highest concentrations of BCM-derived radioactivity were observed in the kidneys and are assumed to be related to the excretory function of these organs. The second highest concentrations were observed in the liver. Concentrations of BCM-derived radioactivity peaked in most tissues at, or prior to, the first time point, 0.25 h. In the liver, peak concentrations were observed approximately 0.5 h post dosing. The rapid decline of BCM-derived radioactivity from most tissues was consistent with the rapid excretion of BCM-derived radioactivity observed in earlier studies (Tables I and II). BCM-derived radioactivity accumulated in only one non-excretory tissue, thymus, where concentrations increased by almost three fold between 0.25 and 4 h post dosing and remained nearly constant for the next 4 h.
Most of the BCM-derived radioactivity in blood was unextractable within the first few minutes following dosing, and parent BCM was virtually undetectable in blood within approximately 5 h. In the present study only about 27% of the radioactivity was extracted from the liver at the 0.25 h time point, and extractable radioactivity in liver decreased to 4% within 4h. At 0.25 h approximately 60% of the radioactivity extracted from liver was parent BCM. This percentage decreased with time until only a trace of parent BCM was detected in the extracts of liver samples taken at 4 and 8 h post dosing. Approximately 85% of the radioactivity was extracted from thymus at the 0.25 h time point and approximately 44% of that radioactivity was parent BCM. However, even though the concentration of BCM-derived radioactivity in the thymus increased with time, extractable radioactivity decreased with time such that by 8 h only 9% of the radioactivity in the thymus was extractable. Further, the relative amounts of parent BCM in the radioactivity extracted from the thymus decreased with time such that only a trace was detected at 4 and 8 h post dosing.
Details on excretion:
Clearance of BCM by male rats
Comparison of data obtained following intravenous vs. oral administration to male rats over a range of doses provided an estimate of the rate and routes by which BCM-derived radioactivity was cleared from the body and the effects of dose on these parameters.

Intravenous administration of [14C]BCM at a presumably non-toxic and non-saturating dose, 1 mg/kg, in order to represent 100% absorption, indicated that BCM-derived radioactivity was rapidly excreted (Table I), primarily in urine, >95%, with a few per cent of the dose being completely metabolized and exhaled as CO2. Approximately 60% of the dose was excreted in 8 h, and excretion was nearly complete within 48 h. Less than 1% of the i.v. dose was recovered in the exhaled volatiles and feces combined.

Oral administration of BCM at lower and higher, but still presumably non-toxic, doses (Table I) indicated that doses in this range were nearly completely absorbed from the gastrointestinal tract and rapidly excreted. Total excretion in either case approached or exceeded 60% within 8 h. The rates and routes of excretion were very similar to those seen following i.v. administration and no evidence of saturation of gastrointestinal absorption or metabolism was observed over the dose range studied. The only statistically significant dose related differences observed were a slightly greater metabolism to 14CO2 and slightly less excretion in urine following administration of the higher dose.

Digestion and analysis of the carcasses 72 h following oral administration of 10mg/kg indicated minimal retention (-1.5% of the dose) of BCM-derived radioactivity. Because about 10% of the dose remains in the body at 24h post dosing, there is the potential for accumulation in a chronic study employing the standard
24-h dose intervals.

Clearance of BCM by male and female mice
Total excretion by both sexes of mice appears to have been slightly slower following an i.v. dose than observed with rats, 79 or 72% vs. 95% in 24 h. Mice may have also excreted a greater portion of the dose in feces than did rats; however, it is likely that this observation reflects, at least in part, the difficulty of obtaining effective separation of urine and feces in studies with mice. Mice also appear to have metabolized a somewhat greater portion of the dose to CO2 than did rats. Both species metabolized a greater portion of the higher dose to CO2. Similar to the data from rats, the total tissues of mice retained less than 1% of the dose 72h following dosing.

Clearance of BCM by rats and mice following dermal administration
Studies of absorption of BCM by male rats and mice following administration of doses of
0.1 or 10 mg/kg to a protected area of skin indicated that, in rats most (13.6-14.3% of the total dose) of the absorbed dermal dose was excreted in urine. In mice of the 10mg/kg dose 12.6% of that dose was recovered in urine. About 9% of the dose was recovered in urine of mice following dermal administration at 0.1 mg/kg.

Clearance of BCM-derived radioactivity following i. v. administration to rats
Following intravenous administration of 1 mg/kg to male rats, decline of BCM from blood was determined by analysis of blood collected from cannulated animals at time points up to 24 h.
Total BCM-derived radioactivity was rapidly removed from blood so that only about 2% of the dose remained in blood at the first time point (data not shown). These data further indicate that by 0.25 h post dosing most of the BCM-derived radioactivity in blood was in the form of metabolites or unextractable, possibly bound, radioactivity. The blood concentrations of both total radioactivity and parent BCM declined rapidly with time; however, the concentration of unextractable radioactivity initially increased to reach a maximum at approximately 2 h post dosing and then slowly declined over the course of the 24-h study.
The unextractable radioactivity accounted for most of the BCM-derived radioactivity at 4 h and at later time points. Similar experiments with female rats and male mice (data not shown) provided very similar results except that the blood of mice contained somewhat less parent BCM.

Metabolite characterisation studies

Metabolites identified:
yes
Details on metabolites:
BCM metabolite isolation and identification
HPLC analysis of urine collected over 24h post dosing from rats administered p.o. or i.v. doses of BCM using the phosphate-buffered Hydrobond AQ system as described in Materials and methods, indicated the presence of five significant metabolites, R1-R5. Neither the pattern nor the relative amounts of the metabolites were greatly affected by the dose or route of BCM administration. Urine from mice dosed with BCM contained three major metabolites, M1-M3. In coelution experiments, M2 appeared to coelute with R4 and 11/13 coeluted with R5.
Incubation of urine from rats receiving an intravenous dose of BCM, 1 mg/kg, with acylase, sulfatase, or B-glucuronidase, failed to alter the chromatographic pattern of metabolites. It was thus assumed that the metabolites were not excreted as conjugates other than from reaction with GSH. HPLC analysis indicated that the major BCM metabolite, metabolite R3, coeluted with thiodiglycolic acid (TDGA), which is a known metabolite of 2-chloroacetaldehyde and 2-chloroethanol. The structure of this metabolite was further confirmed by electrospray MS in negative ion mode and co-chromatography with a known standard of TDGA on the Hydrobond AQ-C8 analytical system described in Materials and methods.

Any other information on results incl. tables

Table I.             Cumulative excretion of radioactivity after[14C]BCM administration to male F-344 rats

 

 

                                                                     Cumulative % dose recovered in

 

 

End of collection period           Urine       Breath volatiles        CO2             Feces             Total

 

Intravenous 1 mg kg-1)

 

 

 

 

 

8h

59.8 ± 8.3

0.18 ± 0.01

2.63 ± 0.95

 

62.6 ± 7.92

24h

90.6 ± 3.4

0.20 ± 0.01

3.27 ± 1.09

0.50 ± 0.12

94.6 ± 2.80

48h

95.7 ± 2.5

0.20 ± 0.02

3.51 ± 1.15

0.73 ± 0.21

100 ± 1.46

72h

96.6 ± 2.3

0.21 ± 0.02

3.66 ± 1.18

0.76 ± 0.21

101 ± 1.29

Oral (0.1 mg kg-1)

 

 

 

 

 

8h

63.2 ± 1.7

0.05 ± 0.01

2.42 ± 0.45

 

65.7 ± 1.7

24h

90.8 ± 0.7

0.06 ± 0.01

3.05 ± 0.58

0.87 ± 0.81

94.7 ± 0.7

48h

93.7 ± 0.6

0.06 ± 0.01

3.27 ± 0.60

1.03 ± 0.80

98.0 ± 0.7

72h

94.6 ± 0.6*

0.07 ± 0.01

3.42 ± 0.60*

1.08 ± 0.82

99.1 ± 0.6

Oral (10 mg kg-1)

 

 

 

 

 

8h

51.8 ± 9.1

0.09 ± 0.02

5.24 ± 1.48

 

57.2 ± 8.3

24h

85.0 ± 1.7

0.11 ± 0.02

6.52 ± 1.86

0.37 ± 0.11

92.0 ± 1.3

48h

89.0 ± 1.7

0.12 ± 0.02

6.94 ± 1.93

0.37 ± 0.10

96.5 ± 1.2

72h

90.0 ± 1.9*

0.12 ± 0.02

7.14 ± 1.97*

0.41 ± 0.16

97.7 ± 1.5

 

n = 4

* Statistically significant difference between the two oral dose levels (p = 0.05)

Table II.         Cumulative excretion of radioactivity 72h after[14C]BCM administration to B6C3F1mice.

 

 

                                                                                      % dose recovered in

 

 

End of collection period           Urine       Breath volatiles        CO2             Feces             Total

 

Intravenous 1 mg kg-1)

male mice

 

 

 

 

 

8h

36.8 ± 26.1

0.91 ± 0.60

6.77 ± 0.91

 

44.5 ± 25.8

24h

53.8 ± 27.9

0.97 ± 0.63

7.51 ± 1.10

16.7 ± 25.7

79.0 ± 11.0

48h

58.6 ± 26.8

1.00 ± 0.65

8.32 ± 1.54

19.5 ± 25.7

87.5 ± 9.9

72h

65.8 ± 26.5

1.01 ± 0.65

8.61 ± 1.55

20.3 ± 25.8

95.7 ± 4.4

Intravenous 1 mg kg-1)

female mice

 

 

 

 

 

8h

27.0 ± 17.2

0.27 ± 0.02

3.52 ± 1.54

 

30.7 ± 16.4

24h

52.0 ± 26.6

0.30 ± 0.03

4.17 ± 1.81

15.2 ± 10.2

71.7 ± 15.8

48h

63.5 ± 25.2

0.31 ± 0.03

4.52 ± 1.98

17.3 ± 11.9

85.6 ± 132.1

72h

71.5 ± 20.5

0.32 ± 0.03

4.70 ± 2.05

17.9 ± 12.5

94.4 ± 8.00

Oral (10 mg kg-1)

male mice

 

 

 

 

 

8h

21.4 ± 19.7

0.08 ± 0.03

10.6 ± 1.3

 

32.0 ± 20.8

24h

41.0 ± 17.1

0.10 ± 0.02

11.6 ± 1.5

20.6 ± 12.7

73.4 ± 9.3

48h

45.6 ± 17.5

0.11 ± 0.03

12.4 ± 1.6

23.7 ± 14.9

81.8 ± 5.5

72h

52.7 ± 17.2

0.11 ± 0.03

12.7 ± 1.6

24.5 ± 15.6

90.0 ± 2.8

Oral (10 mg kg-1)

female mice

 

 

 

 

 

8h

9.35 ± 14.5

NC

7.81 ± 2.04

 

17.2 ± 12.5

24h

34.9 ± 21.7

NC

9.46 ± 2.14

16.5 ± 9.3

60.9 ± 15.9

48h

43.9 ± 24.8

NC

10.3 ± 2.1

20.5 ± 11.5

74.7 ± 16.5

72h

56.8 ± 18.4

NC

10.7 ± 2.2

24.7 ± 14.2

92.2 ± 4.7

 

n = 4.

NC, not collected

Table III.        Absortion of dermal doses of [14C]BMC in male F-344 rats andB6C3F1mice.

 

 

                                                        10 mg kg-1                                                       0.1 mg kg-1     

 

 

                                              Mice                     Rats                       Mice                     Rats             

 

Absorbed

 

 

 

 

Urine

12.59 ± 5.43

13.60 ± 1.88

8.94 ± 1.48

14.33 ± 5.38

CO2

1.10 ± 0.33

0.45 ± 0.15

0.42 ± 0.10

0.36 ± 0.15

Feces

1.75 ± 1.01

0.60 ± 0.57

a

0.27 ± 0.08

Tissues

1.63 ± 1.80

0.55 ± 0.13

b

0.51 ± 0.13

Dose site

1.25 ± 1.59

0.24 ± 0.09

b

0.25 ± 0.18

Total Absorbed

18.30 ± 3.78

15.44 ± 2.55

9.36 ± 1.40

15.73 ± 5.82

Unabsorbedc

19.33 ± 9.00

52.72 ± 10.09

7.23 ± 1.98

53.65 ± 9.97

Volatilized

35.22 ± 15.63

18.73 ± 1.18

24.23 ± 4.06

18.78 ± 4.80

Total recovery

72.87 ± 9.45

86.88 ± 12.26

40.82 ± 5.87

88.15 ± 14.60

 

n = 4. Data are mean ± SD of percentage dose recovered. Excreta were collected for 24 h post dosing. Tissues were sampled at 24 h post dosing.

aNo feces samples were collected.

bNo tissue samples were collected.

cRadioactivity recovered in the protective appliances and skin washes.

Table IV.       Distribution of BCM-derived radioactivity in tissues of male rats following i.v. administration of [14C]BCM

 

Tissue

                               0.25 h                         

0.5 h                  

1.0 h                         

2.0 h                          

4.0 h                          

8.0 h

Adipose

1760 ± 214

1520 ± 221.

663 ± 84.7

316 ± 21.2

237 ± 187

41.4 ± 4.39

Blood

610 ± 18.6

529 ± 76.6

383 ± 53.2

343 ± 129

274 ± 41.0

154 ± 38.6

Brain

50 ± 11.4

197 ± 31.4

103 ± 10.7

69.0 ± 8.37

74.8 ± 5.41

41.1 ± 4.83

Heart

481 ± 12.8

401 ± 72.5

253 ± 12.2

200 ± 46.9

128 ± 24.9

47.8 ± 6.42

Kidney

19 900 ± 1080

20 700 ± 88.1

16 000 ± 1400

9930 ± 2320

3930 ± 1810

1000 ± 60.2

Liver

2420 ± 77.9

2800 ± 237

1790 ± 130

1670 ± 135

1200 ± 218

532 ± 78.0

Lung

979 ± 71.0

889 ± 81.7

559 ± 65.0

783 ± 614

287 ± 39.9

149 ± 13.6

Muscle

379 ± 11.1

415 ± 282

134 ± 18.4

82.2 ± 23.2

76.8 ± 27.9

30.5 ± 15.7

Skin

641 ± 5.18

413 ± 51.1

307 ± 12.3

371 ± 152

334 ± 118

214 ± 66.5

Spleen

396 ± 9.13

374 ± 26.1

397 ± 24.8

571 ± 9.35

476 ± 26.2

207 ± 13.5

Testis

374 ± 63.8

277 ± 40.5

276 ± 22.3

393 ± 23.9

336 ± 28.7

104 ± 4.43

Thymus

402 ± 78.4

278 ± 72.7

410 ± 32.0

842 ± 57.5

1140 ± 123

1040 ± 157

% Dose in tissues

80.40 ± 2.33

70.38 ± 2.55

80.40 ± 2.33

33.11 ± 3.87

23.70 ± 5.53

10.30 ± 1.77

 

Data are ng BCM equivalents per gram tissue and are calculated based on the specific activity of the parent compound; mean ± SD; n = 3. Dose level was 1 mg kg-1.

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no bioaccumulation potential based on study results
The test substance is rapidly absorbed and excreted after oral and dermal exposure. The major metabolite (about 40% of the dose) of BCM in rat was isolated and identified as thiodiglycolic acid (TDGA).
Executive summary:

bis(2-Chloroethoxy)methane (BCM) is used primarily as a precursor in the synthesis of polysulfide elastomers. After administration of [ 14C]BCM , radioactivity is readily absorbed from the gastrointestinal tract and moderately absorbed through skin. Following absorption, BCM-derived radioactivity is rapidly distributed to all tissues, rapidly metabolized and excreted primarily in urine. Minimal effects of sex, species or dose in the range studied (0.1-1 0 mg kg) were observed on the fate of BCM in rats and mice after all routes of administration. The major metabolite (about 40% of the dose) of BCM in rat was isolated and identified as thiodiglycolic acid (TDGA) indicating that the ether linkage of BCM is cleaved to form 2-chloroethyl fragments that may be further metabolized to 2-chloracetaldehyde, conjugated with glutathione and the latter subsequently metabolized to TDGA. 2-chloroacetaldehyde has also been shown to be cardiotoxic, possibly accounting for BCM cardiotoxicity observed in repeated dose studies.