This study presents an improved and validated method for quantifying six common plastic polymers (polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), poly(methyl methacrylate) (PMMA), polypropylene (PP), and polystyrene (PS)) in human whole blood samples using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The method includes stringent quality assurance and quality control procedures, such as the use of quality control samples and continuous monitoring of batch analyses to ensure data reliability. The Py-GC-MS conditions were optimized to enhance method sensitivity and selectivity. Recovery experiments showed high accuracy and precision, with values ranging from 68 to 109% for quality control samples. Applying this method to 68 whole blood samples, plastic polymers were detected in 64 samples, with PE as the predominant polymer, followed by PVC, PET, and PMMA. In 17 blood samples, polymer concentrations exceeded the limit of quantitation, with a mean of 1070 ng/mL for the summed polymer concentrations, ranging between 170 and 2490 ng/mL. The mean of the sum of polymers across all blood samples (n=68) was 268 ng/mL. These findings highlight the need for further research to comprehensively quantify micro and nanoplastics (MNPs) in human matrices, considering their potential health implications. The study also emphasizes the importance of rigorous quality control measures to ensure accurate and reliable data. The method was applied to 68 whole blood samples, and plastic polymers were detected in 64 out of the 68 samples, with PE being the most frequently detected polymer. The mean of the sum of polymers quantified in blood was 1070 ng/mL, ranging from 170 to 2490 ng/mL. The study confirms the presence of plastic polymers in human blood and underscores the need for further research to fully understand the implications of MNPs in human health.This study presents an improved and validated method for quantifying six common plastic polymers (polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), poly(methyl methacrylate) (PMMA), polypropylene (PP), and polystyrene (PS)) in human whole blood samples using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The method includes stringent quality assurance and quality control procedures, such as the use of quality control samples and continuous monitoring of batch analyses to ensure data reliability. The Py-GC-MS conditions were optimized to enhance method sensitivity and selectivity. Recovery experiments showed high accuracy and precision, with values ranging from 68 to 109% for quality control samples. Applying this method to 68 whole blood samples, plastic polymers were detected in 64 samples, with PE as the predominant polymer, followed by PVC, PET, and PMMA. In 17 blood samples, polymer concentrations exceeded the limit of quantitation, with a mean of 1070 ng/mL for the summed polymer concentrations, ranging between 170 and 2490 ng/mL. The mean of the sum of polymers across all blood samples (n=68) was 268 ng/mL. These findings highlight the need for further research to comprehensively quantify micro and nanoplastics (MNPs) in human matrices, considering their potential health implications. The study also emphasizes the importance of rigorous quality control measures to ensure accurate and reliable data. The method was applied to 68 whole blood samples, and plastic polymers were detected in 64 out of the 68 samples, with PE being the most frequently detected polymer. The mean of the sum of polymers quantified in blood was 1070 ng/mL, ranging from 170 to 2490 ng/mL. The study confirms the presence of plastic polymers in human blood and underscores the need for further research to fully understand the implications of MNPs in human health.