Although the exact cause of most of patients with PD remains unknown, recent studies suggest that a combination of genetic and environmental risk factors may play a key role in the development of the disease , , . Typically, monogenic PD comprises five dominantly inherited forms (SNCA, LRRK2, VPS35, RAB32 and CHCHD2) and three recessively inherited forms (PRKN, PINK1, and PARK7) , . Mitochondrial dysfunction may occur already in the early stages of PD pathogenesis and plays a crucial role in both sporadic and familial forms of the disease , . Gene variants of Leucine-rich repeat kinase 2 (LRRK2) are the most common monogenic cause of PD, accounting for 1-2% of all cases , , , . Most of the LRRK2 pathogenic variants result in increased kinase activity of the LRRK2 protein, leading to mitochondrial dysfunction and promoting inflammatory responses that may result in chronic neuroinflammation and gut inflammation , . In addition to PD, LRRK2 has been linked to inflammatory diseases including Crohn's Disease, leprosy and tuberculosis , . While the p.G2019S pathogenic variant of LRRK2 is the best known and most common, not all carriers of this variant will develop PD, a phenomenon termed "reduced penetrance" , , , . Importantly, the penetrance is age-dependent and differs across geographic regions. For example, in Tunisia, 61% of LRRK2 p.G2019S carriers developed PD by the age of 60 years, and 86% by the age of 70. In contrast, in Norway, only 20% of carriers developed the disease by age 60, and 43% by age 70 , . This suggests that factors beyond genes, such as lifestyle or environment, may play a crucial role in triggering the onset of the disease . Various environmental factors have been previously associated with an increased risk of PD, including the exposure to metals (e.g., Cu, Fe and Zn) and pesticides (e.g., rotenone and paraquat) . In contrast, smoking, caffeine consumption, and the use of anti-inflammatory drugs have been linked with a reduced PD risk , . The LRRK2/Luebeck International Parkinson's Disease Study (LIPAD) cohort is one of the largest multinational cohorts of genetic PD, focused on LRRK2-associated PD and healthy LRRK2 pathogenic variant carriers aiming to identify modifiers of LRRK2 penetrance . This study includes the household dust from selected LIPAD cohort participants to determine whether this can potentially reveal potential chemical exposures and taxa of interest that may influence LRRK2 penetrance.