Microplastics, typically smaller than 5 mm (and in some cases less than 1 μm), are now widespread environmental pollutants that originate from both primary sources, such as personal care products and industrial abrasives, and secondary sources formed through the degradation of larger plastic materials. This chapter examines microplastic detection methods, environmental distributions, and human health implications. Fourier transform infrared (FTIR) spectroscopy serves as the primary analytical tool for microplastic identification, with ATR-FTIR, micro-FTIR (μFTIR) imaging, transmission, and reflection modes enabling the detection of particles across various matrices. Microplastics contaminate all environmental compartments; marine systems accumulate particles in subtropical gyres; freshwater systems show variable concentrations linked to human activities; drinking water contains detectable levels in both tap and bottled sources; and agricultural soils accumulate particles through sewage sludge and plastic mulch. Microplastics have also been found in blood, placental tissue, and feces, and humans are exposed through ingestion, inhalation, and skin contact. An estimated 39,000–52,000 particles are consumed by humans annually, which raises questions regarding chemical contamination, cellular toxicity, and gastrointestinal inflammation. FTIR-based detection methods are essential for monitoring contamination patterns and human exposure, highlighting the urgent need for regulatory frameworks and mitigation strategies to address this growing environmental and public health challenge.