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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics in vivo
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1996
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well described and well conducted in vivo study performed in humans, giving valuable data about absorption and excretion of several terpenes after inhalation exposure.
Cross-referenceopen allclose all
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
1996

Materials and methods

Objective of study:
absorption
excretion
Principles of method if other than guideline:
Absorption and excretion rates of alpha-pinene, beta-pinene and 3-carene after inhalation exposure to turpentine vapour in human volunteers.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
Name of test material (as cited in study report): turpentine
Source: Swedish turpentine, Alcro Beckers
Radiolabelling:
no

Test animals

Species:
human
Sex:
male
Details on test animals and environmental conditions:
Eight healthy men, not occupationally exposed to solvents, with a mean (range) age of 28 (18-37) years and weight of 75 (62-83) kg participated in the study. All were nonsmokers and they were instructed to refrain from alcohol and activities that could cause exposure to organic solvents during the preceding two days and throughout the experiment.

Administration / exposure

Route of administration:
inhalation: vapour
Vehicle:
unchanged (no vehicle)
Details on exposure:
The subjects were exposed to turpentine for two hours (450 mg/m3 (75 ppm)) during light physical exercise (50 W on a bicycle ergometer). The
exposure was conducted in an exposure chamber. The volume of the chamber was 12 m3. The air was changed 10 times/h. To prevent the solvent from leaking from the chamber into the surroundings the inlet flow was 115 m3/h and the outlet flow was 135 m3/h. The solvent was injected into the inflowing air stream by means of a high-performance liquid chromatography pump (Gilson 302). The mean temperature in the chamber was 21°C and varied by less than 2.5°C during a two hour exposure to turpentine and between different days.
Duration and frequency of treatment / exposure:
2 h, once
Doses / concentrations
Remarks:
Doses / Concentrations:
450 mg/m3 (75 ppm)
No. of animals per sex per dose:
8
Control animals:
no
Positive control:
None
Details on study design:
A low concentration of 3-carene, 10 mg/m3, was used as a control. The control concentration was chosen as low as possible so that no effect was to be expected, but the subjects could still smell the solvent.
The workload 50 W was chosen to imitate the physical activity generally found in light industries.
Details on dosing and sampling:
The solvent concentration in the air of the chamber was continuously monitored at atmospheric pressure by an infrared spectrophotometer (Miran 80) equipped with a 20 m thermostatically controlled (45°C) gas cell. Measurements of monoterpenes in the air of the chamber were made at 3.39 µm with 3.6 µm as the reference wavelength. The concentration of monoterpenes varied by less than 2% during the two hour exposure of turpentine and less than 3% between different days.

Air sampling: at four regular time intervals during the exposure exhaled air was individually collected in polyester laminated aluminium foil bags (about 20 L) for about four minutes each. Exhaled air samples were also collected after exposure (5, 15, 25, 85, 150, and 230 minutes after the end of exposure). The volume of the expired air was measured with a balanced spirometer and the concentrations of monoterpenes were analysed on a gas chromatograph (Carlo Erba, Fractovap 2350) equipped with a flame ionisation detector and a polar column (Supelcowax 10, 30 m, 0-75 mm inner diameter).

Blood sampling: arterial capillary blood (200 µL) was collected from a prewarmed fingertip at selected intervals during the exposure and up to 21 h after end of exposure, for measurement of monoterpenes in blood. Blood sampling during exposure was taken by the subject holding out one hand through a closable hole in the wall. Blood samples were collected in heparinised capillary tubes (2 x 100 µL) and transferred to gas tight head space vials (22-4 mL) which were capped immediately with Teflon lined membranes. The samples were kept for 20 minutes at 37°C before analysis.
The headspace of the blood samples was analysed on a gas chromatograph (Perkin Elmer 8700) equipped with a head space autosampler (Perkin Elmer HS-101), a polar column (Supelcowax 10, 30 m, 0-75 mm inner diameter), and a flame ionisation detector. The concentration of monoterpenes in the blood was measured by comparison with individual standard curves prepared in the same concentration range by adding monoterpenes to blood samples taken before the exposure.
Statistics:
None

Results and discussion

Preliminary studies:
None

Toxicokinetic / pharmacokinetic studies

Details on absorption:
The relative net uptakes of the total inhaled alpha-pinene, beta-pinene, and 3-carene averaged 62%, 66%, and 68% respectively (% of total inhaled).
Details on distribution in tissues:
None
Details on excretion:
Between 2% and 8% of the net uptake was excreted unchanged in the expired air after the end of exposure. The mean blood clearance 21 h after exposure (CL21h) of alpha-pinene, beta-pinene and 3-carene, were 0.8, 0.5, and 0.4 L/kg/h, respectively. The mean half lives (t1/2) of the last phase of alpha-pinene, beta-pinene, and 3-carene averaged 32, 25, and 42 h, respectively.

Metabolite characterisation studies

Metabolites identified:
not measured
Details on metabolites:
None

Any other information on results incl. tables

The mean total concentration of the monoterpenes in the air of the chamber from all the turpentine exposures was 449 mg/m3, with a relative SD of 1-4%, based on air concentrations from four different occasions at each exposure.

If the assumption is made that the turpentine consists of alpha-pinene, beta-pinene, and 3-carene, the proportions of the vapour were about 54%, 11%, and 35%, respectively.

Table 1: Mean (SD) experimental results ofsome physiological and toxicokinetic vaiables from two hour inhalation exposure to 450 mg/m3 of turpentine during physical exercise at a workload of 50 W (also, results from previous single exposure to alpha-pinene and 3-carene are presented)

 

Alpha-pinene

Beta-pinene

 

Exposure to turpentine

3-carene

 

Exposure to turpentine

Exposure to alpha-pinene

Exposure to alpha-pinene

Exposure to turpentine

Exposure to 3-carene

Exposure to 3-carene

Air concentration (mg/m3)

242 (3.3)

455 (5.3)

225 (5.1)

49 (0.67)

157 (2.1)

451 (5.8)

228 (5.8)

Net uptake (% of total inhaled)

62 (5.3)

58 (5.3)

60 (3.9)

66 (5.8)

68 (7.5)

71 (4.7)

70 (4.4)

Respiratory elimination after exposure (% of net uptake)

3.8 (1.1)

7.7 (3.1)

5.7 (5.7)

5.0 (5.8)

2.4 (1.5) *

4.8 (1.2)

1.9 (1.5)

Concentration at steady state (30 min before end of exposure) (µmol/L)

9.0 (0.75)

19 (3.6)

9.6 (1.9)

2.6 (0.29)

9.9 (0.89)

25 (0.92)

12 (1.4)

* P<0.05, Student's t test v. pure 3-carene (450 mg/m3)

Table 2: mean (SD) apparent CLs and t1/2s of alpha-pinene, beta-pinene, and 3-carene from two hour inhalation exposure to 450 mg/m3 of alpha-pinene, 3-carene or turpentine during physical exercise at a workload of 50 W

 

Alpha-pinene

Beta-pinene

 

Exposure to turpentine

3-carene

 

Exposure to turpentine

Exposure to alpha-pinene

Exposure to turpentine

Exposure to 3-carene

CL4h (L/kg/h)

1.6 (0.3)

1.4 (0.31)

0.8 (0.3)

1.0 (0.2)

0.3 (0.1)

CL21h (L/kg/h)

0.8 (0.09) §

1.1 (0.2)

0.5 (0.3) §

0.4 (0.1) §

0.9 (0.3)

t1/2 terminal (h)

32(18)

12 (4)

25 (18)

42 (23)

30 (22)

§ four subjects due to analytical problems resulting in problems calculating AUC

Applicant's summary and conclusion

Conclusions:
Interpretation of results (migrated information): no data
The mean relative uptakes of alpha-pinene, beta-pinene, and delta-3-carene were 62%, 66%, and 68% respectively, of the amount inhaled. Between 2% and 5 % of the net uptake was excreted unchanged in the expired air after the end of exposure. The mean blood clearance 21 h after exposure (CL21h) of alpha-pinene, beta-pinene and delta-3-carene, were 0.8, 0.5, and 0.4 L/kg/h, respectively. The mean half lives (t1/2) of the last phase of alpha-pinene, beta-pinene, and delta-3-carene averaged 32, 25, and 42 h, respectively.
Executive summary:

In this study, eight male volunteers were exposed to 450 mg/m3 turpentine by inhalation (2 h with physical exercise workload of 50 W) in an exposure chamber and the extent of alpha-pinene, beta-pinene and delta-3-carene inhaled as well as their excretion rates from blood were investigated.

The mean relative uptakes of alpha-pinene, beta-pinene, and delta-3-carene were 62%, 66%, and 68% respectively, of the amount inhaled. Between 2% and 5 % of the net uptake was excreted unchanged in the expired air after the end of exposure.

The mean blood clearance 21 h after exposure (CL21h) of alpha-pinene, beta-pinene and delta-3-carene, were 0.8, 0.5, and 0.4 L/kg/h, respectively. The mean half lives (t1/2) of the last phase of alpha-pinene, beta-pinene, and delta-3-carene averaged 32, 25, and 42 h, respectively.

The last phase of the t1/2s tended to be longer after exposure to turpentine than monoterpenes. The total blood clearance CL21h of delta-3-carene found in this study was lower, and CL4h of delta-3-carene was significantly lower than the values obtained from similar exposure to pure delta-3-carene.