Fertilizers and Human Health-A Systematic Review of the Epidemiological Evidence

Background: Fertilizers are widely used to supply nutrients to crops, thereby increasing yields and soil fertility. However, the effects of their production and application on human health through occupational, residential, and environmental exposure remain unclear. Objective: To conduct a systematic review of epidemiological studies on the association between exposure to fertilizers and health-related outcomes. Methods: We searched in PubMed, Scopus, and Web of Science for cohort, case-control, cross-sectional, and ecological studies (up to May 2024) related to exposure to fertilizers and any reported human health endpoints across all age groups, without language or geographical limitations. Data were extracted for population and study characteristics, type of fertilizer used, exposure assessment, sample size, outcome and its definition, effect estimate, and quality characteristics from the eligible studies, and they were descriptively synthesized. Results: We found 65 eligible publications, with 407 postulated associations. Forty-six publications (321 associations) assessed exposure to inorganic fertilizers, and nineteen studies (93 associations) assessed organic fertilizers. Exposure assessed was related to occupation, residence, and/or proximity. The assessed outcomes were diverse, with considerable harmonization challenges. Inorganic fertilizers have been associated with an increased risk of cancerous outcomes in a small number of studies with methodological limitations and low replication validity, while organic fertilizers have been associated with infections and diarrhea. Conclusions: The epidemiological evidence suggests possible associations between inorganic fertilizers with solid organ tumors and hematological malignancies and organic fertilizers with infections and diarrhea. However, the available evidence is limited, and heterogeneity prevails. Further research is needed to enlarge the evidence base and increase the replication validity and robustness of the results.