**Background:** Volatile organic compounds (VOCs) are ubiquitous indoor and outdoor air pollutants from both natural and anthropogenic sources. In carpentry workshops, paint solvents release hazardous VOCs such as benzene, toluene, ethylbenzene, and xylenes (BTEX), as well as formaldehyde, which is classified as a Group 1 human carcinogen by the IARC. Inhalation is the primary route of exposure, and chronic exposure has been linked to asthma, cardiovascular disease, COPD, and cancer. While many studies have measured VOCs in breath, fewer have quantified them directly in blood. This study aimed to develop a sensitive, validated method for measuring 38 VOCs in whole blood at parts-per-trillion (ng/L) levels using headspace solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS), and to apply this method to assess exposure among carpentry workers, nearby residents, and school students in the Palestinian village of Deir Ballout—the first study of its kind in Palestine.
**Methods:** The study was conducted in Deir Ballout, a village in the Salfit Governorate (population 4,650), located 41 km south of Nablus. Indoor air samples were collected from four locations: the carpentry shop, a residential house 20 m west, another house 40 m north, and an elementary school 200 m north of the shop. Passive VOC samples were collected using thermal desorption adsorbent tubes over 24 hours (sampling rate 10 mL/min, total volume 14.4 L) following EPA TO-17 methodology. The 24-hour average indoor temperature was 23.3 ± 0.4 °C, relative humidity 51.6 ± 14.5%, and average air exchange rate 0.68 ± 0.50 h⁻¹. Thirty healthy volunteers were recruited: 10 male carpentry workers (5 heavy smokers, mean age 27 years), 10 residents living within 30 m of the shop (2 smokers, 5 females), and 10 elementary school students aged 12–16 years. Venous blood samples were collected in specially prepared gray-top Vacutainers containing potassium oxalate and sodium fluoride, with butyl rubber stoppers roasted in a vacuum oven at 80 °C for 17 days to eliminate VOC residue. Blood samples (1 mL whole blood + 1 mL water) were analyzed using HS-SPME-GC-MS with a 75 μm Carboxen/PDMS fiber, sampling for 2 min at 500 rpm stirring, desorption at 250 °C for 0.5 min, and equilibration at 60 °C for 30 min. Calibration standards were prepared at seven concentration levels (0.010, 0.030, 0.100, 0.300, 1.00, 3.00, and 10.0 μg/L). Method detection limits (MDLs) ranged from 0.001 to 0.5 μg/L depending on the analyte. Quality control included four QC samples per batch, blind proficiency testing using EPA 524 rev A mix, and blank water analysis for contamination monitoring.
**Key Results:** A total of 38 VOC compounds were detected and quantified in both blood and indoor air samples. Blood concentrations ranged from 3 ng/L (trichloroethene) to 270 ng/L (toluene-2,4-diisocyanate). The most abundant compounds in blood were toluene (83 ± 0.321 ng/L), m/p-xylene (68 ± 0.328 ng/L), ethyl acetate (65 ± 0.113 ng/L), propanal (65 ± 0.121 ng/L), and acetonitrile (57 ± 0.105 ng/L). In indoor air, concentrations ranged from 4.7 ng/L (bromodichloromethane) to 291.5 ng/L (toluene-2,4-diisocyanate). Over 80% of quantified species had mean blood concentrations below 50 ng/L. Benzene levels in smokers' blood were approximately 10 times higher than in nonsmokers (14–20 ng/L vs. 9–14 ng/L). Toluene levels were 78–87 ng/L in smokers vs. 82–98 ng/L in nonsmokers. Acetonitrile was also elevated in smokers (52–63 ng/L) compared to nonsmokers (41–49 ng/L). Several hydrocarbons were more abundant in room air than in blood, suggesting low blood solubility. Two aldehydes (2-propenal and propanal) were detected in about 50% of blood samples. Calibration curves showed strong linearity (correlation values >0.99). Blood LOD values ranged from 0.01 to 280 nmol/L.
**Clinical Implications:** This study demonstrates that carpentry paint solvents are a significant source of VOC exposure for both workers and nearby residents, with blood levels of several compounds (e.g., toluene-2,4-diisocyanate at 270 ng/L) exceeding typical background levels. The finding that smoking substantially elevates blood VOC concentrations (e.g., 10-fold increase for benzene) underscores smoking as a critical confounder in exposure assessment. The validated SPME-GC-MS method provides a sensitive, reproducible approach for biomonitoring VOCs at parts-per-trillion levels, which can be applied to future epidemiological studies. The results support the need for improved ventilation in carpentry workshops, use of personal protective equipment, and public health interventions to reduce indoor VOC exposure, particularly in communities near occupational sources. The study also highlights the importance of regulatory monitoring in regions where such data have been lacking.