1. Benzene Exposure Due to Jet Fuel A1 in Civil Aircraft Maintenance
Results of a pilot study
Dr M. Klerlein, F. Jeandel, P. Dauphin, C. Brossin, M.A. André-Lesage
Air France Industries
Occupational Physician

2. Benzene and jet fuel in aircraft maintenance
Several studies show true low level benzene exposure in aircraft maintenance
Levels are really low : range ppm to 0.01 ppm
Studies conducted in military aircraft maintenance settings (mainly in US) show significant rise of some jet-fuel biomarkers after medium to high exposition
No definite conclusion about true health effects on aircraft maintenance workers specifically due to benzene
No overall mortality excess, no specific mortality excess for haematopoietic diseases
Few studies report association between jet fuel exposure and vestibular functionnalities or reproductive effects
In France, two cases of haematopoietic malignancies accepted for occupational disease compensation.
This latter point led Air France Industries to build an industrial hygiene survey to evaluate the chemical hazard of jet fuel exposure during aircraft maintenance activities

3. Main points of the Air France Industries « EKMA » study design
EKMA stands for « Kerosene Exposure in Aircraft Maintenance »
Part 1 : Chemical analysis of jet fuel samples obtained from worldwide locations
GC-MS analysis of 12 jet fuel samples
Part 2 : Industrial hygiene assessment of the toxicity kinetic of the aircraft tank atmosphere from the opening time to 24 h after ventilation beginning
GC-MS analysis of air samples collected inside B747 jet fuel wing tanks
Part 3 : Biometrologic survey of a representative sample of AFI aircraft mechanics performing various task exposed to jet fuel odor or droplets projections
Urinalysis pre- and post-shift of t-t-MA (pilot study), SPMA (main study), 1- and 2- naphthol (pilot and main study)
86 exposed workers and 7 non exposed controls

4. Part 1 : Chemical assessment of Jet Fuel A1
12 samples of jet fuel directly withdrawn from aircrafts tanks, when back to our Roissy CDG mainbase
Detection and quantification of 5 compounds of interest :
Benzene
Toluene
Xylene
EGME (anti-icing + biocide additive )
Naphthalene (used as surrogate of jet fuel exposure marker in numerous studies)
Analytical method : GC-FID & GC-MS - Column DB5 60 m long x 0.25 mm internal diameter (film thickness 0.25µm)
Quantification using internal standards and area-under-curve ratio

5. GC-MS Results : 1. Civil aircrafts
All results in % of ponderal mass (w/w)
No EGME detected

6. GC-MS results : 2. Military aircrafts & Miscellaneous jet fuel contaminated fluids
All results in % of ponderal mass (w/w)
No EGME detected

7. Main learnings of the Part 1
Benzene content seems to be extremely low in the « raw » jet fuel
Therefore, benzene exposure due to jet fuel should be quite negligible for the main occupations performed in aircraft maintenance
One exception could occur when working in confined space polluted by jet fuel e.g. aircraft tank sealing/desealing tasks
Naphthalene is present in jet fuel A1 but at quite low concentration.
Use urinary naphthalene metabolites (i.e. 1- & 2- naphthol) as a jet fuel surrogate for exposure assessment could be not really adapted in the aircraft maintenance environment

8. Study, part 2 : Wing Tank Entry

9. 15 mn after opening (2 mn ventilation)
Study, part 2 : Toxicity kinetic of the aircraft atmosphere from opening to 24 h ventilation
Tank opening
15 mn after opening (2 mn ventilation)

10. Wing Tank pollution : results
Very rapid decrease of main pollutants concentration after wing tank ventilation
Extremely low level of benzene after 2 minutes ventilation :
22.97 mg/m3 (700 % french TWA)
0.15 mg/m3 (4 % french TWA) after 2 mn ventilation
small re-increase to mg/m3 (17 % french TWA) after 2 hours ventilation
then under detection limit of 0.01 mg/m3 from 4 hours to 24 hours ventilation.
One air sample coming from less ventilated areas during drying task show very low but detectable value of benzene around 0.06 mg/m3, even after 4 hours ventilation

11. Part 3 : Biometrologic study
Pre- & Post shift urinalysis of :
trans,trans-muconic acid (biomarker of benzene exposure) – only in the pilot study
S-phenyl mercapturic acid (biomarker of benzene exposure) – only in the main study
1 & 2 naphthols (biomarkers of naphthalene, used as a surrogate of jet fuel exposure)
Coupling with passive air sampling during the whole shift with determination of atmospheric concentration of benzene – naphthalene – C9 to C12 aliphatic hydrocarbons (results not presented here)
Subjects :
Pilot study : 16 aircraft mechanics volunteers, only for high exposure shifts. Urinanalysis only post-shift
Main study : 93 volunteers included and categorized in 4 exposure groupes :
Low exposure (only odor of jet fuel, no direct exposure during shift)
Intermediate exposure (occasional task involving jet fuel during shift)
High exposure (whole shift in contact with jet fuel – jet fuel tank entry)
Controls

12. Part 3 : Subjects
Exposed workers are only men.

13. Study, part 3 : Jet Fuel exposure
Outdoor, low exposure
Inside tank, high exposure
Outdoor refueling, intermediate exposure
Workshop fuel pump repair, intermediate exposure
Workshop, low exposure

14. Study,part 3 : Methods
Urine samples were collected immediately pre- and post shift:
For naphthols and t,t-MA, using a specific device designed for storing samples before analysis (URIPREL® , developed by INRS, the french OSHA)
For SPMA ,using pre-acidified aliquots
Analysis techniques
t,t-MA and naphthols: desorption of the URIPREL kit (methanol) then hydrolysis, followed by direct injection to an HPLC system with fluorescent detection. (INRS & Toxilabo – France)
SPMA : immunoassay (ELISA) using PMA (AB Biomonitoring – UK)
Statistical Analysis
Due to the high proportion of values below detection limit (naphthols – t,t-MA) we used the NADA macros for Minitab developped by Dennis R. Helsel for left censored data (see
Macro used :
KMSTATS.mac : summary statistics for left-censored data using the Kaplan-Meier method.
PMLE.mac (paired t-test for left-censored data using maximum likelihood)
URIPREL®

15. Study,part 3 : Pilot study biomarkers results
Compared to non smokers reference values, no difference could be determined
All biomarkers were significantly below the reference values for non exposed smokers

16. Study,part 3 : Main study biomarkers results (all values in µg/g creatinine)

17. Study,part 3 Main study : Analysis of BEI results
All results of non smokers are significantly below smokers values
References values valid for unexposed people living in european urban areas

18. Main study : analysis results
Post-shift vs pre-shift datas :
No difference post and pre-shift, except for SPMA (only seen for the overall exposed group – not seen in the exposure subgroups : possible lack of power for subgroups tests).
Comparison to reference values :
Post-shift SPMA values well below ACGIH standard (p < 0.001)
Pre and post-shift SPMA values below reference values for urban area with atmospheric benzene pollution around 9 µg/m3.
All urinary naphthol post shift values significantly below relevant references values for urban areas
Other findings :
High number of value below detection limit for urinary naphthols
Very significant differences between smokers and non-smokers.

19. Conclusions
In common aircraft maintenance operations, exposure to benzene may be mostly negligible
Using naphthalene urinary metabolites as a surrogate for jet fuel exposure requires very high sensitivity analysis, not allowed through HPLC with fluorescent detection.
Compared to military aircraft maintenance, civil aircrafts tanks maintenance seems to be less exposing for jet fuel toxic components. This could be explained by less skin contacts (no foams inside tanks) and systematic use of long term tank ventilation before entry.

20. Thank you for attention !