Acetylcholinesterase and neuropathy target esterase activities in 11 cases of symptomatic flight crew members after fume events

ABSTRACT

In modern aviation, so-called fume events such as exposure to an unknown mixture of chemicals introduced into the aircraft cabin with bleed air drawn off at the engines may occur. Human exposure may result in (neuro)toxic symptoms described as so-called “aerotoxic syndrome.” Currently, among other agents organophosphates (OP) are regarded as a likely cause of the observed adverse effects. After fume events 11 flight crew members (9 female/2 male; ages 23–58 yr) were admitted for a medical examination within 5 d post exposure. Individual acetylcholinesterase (AChE) and neuropathy target esterase (NTE) activities were determined. Anamnesis and clinical findings confirmed prominent symptoms of an intoxication, including headache, cognitive difficulties, and neurological disorders, among others. Patient AChE activities ranged from 37 to 50 U/g hemoglobin (reference values: 26.7–50.9 U/g hemoglobin). Ten individuals showed NTE activities ranging from 3.14 to 6.3 nmol phenyl valerate/(min × mg protein) (reference values: 3.01–24), with one patient exhibiting low NTE activity of 1.4. Biochemical effect monitoring was applied to encompass a broad range of AChE-inhibiting compounds such as OP, carbamates, and isocyanates, or to detect inhibition of NTE. The measured AChE activities indicated a subordinate contribution of OP or related compounds to the observed symptoms. All noted NTE activities were clustered at low levels. Our data suggest a likely inhibition of NTE activities in patients after fume events, which warrants further investigation. The observed symptoms may be linked to known chemical compounds in fume events, and it is not possible to infer a direct correlation between manifestations and AChE -inhibiting compounds at this time.

Acknowledgments

The authors thank Andrea Kristen, MSc psychology, for her support in the medical examinations.