Salts of phosphonic acid (sodium or potassium phosphonate) or its ester fosetyl are highly effective systemic fungicides, which not only exhibit fungistatic activities, but also stimulate the natural defence systems of the plants against pathogens. Since EU legislation has approved potassium and sodium phosphonate as fungicides in 2013 and 2014, they are no longer permitted in organic agriculture. As a result, even minor contents of phosphonate in organic food samples are interpreted as an indication of a not permitted fungicide treatment. A maximum level of 0.01 mg/kg applies for food for infant nutrition. Here we present evidence from the scientific literature that phosphonate is also a natural compound, which occurs in significant amounts in the environment and is produced and consumed by microorganisms within the biogeochemical phosphorus cycle. Further potential sources for this chemical in the environment apart from agricultural fungicide applications are organophosphonates, as phosphonate occurs as a byproduct during their industrial production or during their microbial degradation in effluents from industry and households. An evaluation of Eurofins results from the analysis of phosphonate from 2017 to 2022 with methods achieving a limit of quantification (LOQ) of 0.01 mg/kg reveals that the compound was detected in 40.63% of all samples from organic and 43.42% from conventional agriculture, and in over 90% of organic samples of chickpeas, lentils, buckwheat, peanuts and wine. Furthermore, 97.3% of organic mushroom samples contain the compound and animal manure or compost used for cultivation is a potential source of the chemical. Consequently, other causes for phosphonate in food products than fungicide applications must be taken into account as well. Analysis of the ratio of the stable oxygen isotopes ¹⁸O and ¹⁶O was successfully applied to detect applications of mineral sulphur fertilizer in organic agriculture. Similarly, it might be also a promising tool to differentiate between phosphonate produced industrially and from natural sources.

膦酸盐（膦酸钠或膦酸钾）或其酯乙膦是高效的内吸性杀菌剂，不仅具有抑制真菌的活性，而且还能刺激植物对病原体的天然防御系统。由于欧盟立法已于 2013 年和 2014 年批准膦酸钾和膦酸钠作为杀菌剂，因此它们不再被允许用于有机农业。因此，即使有机食品样品中的少量膦酸盐也被解释为不允许使用杀真菌剂处理。0.01 mg/kg 的最大水平适用于婴儿营养食品。在这里，我们提供来自科学文献的证据，表明膦酸盐也是一种天然化合物，其在环境中大量存在，并在生物地球化学磷循环中由微生物产生和消耗。除了农业杀真菌剂应用之外，环境中这种化学物质的其他潜在来源是有机膦酸盐，因为膦酸盐在其工业生产过程中或在工业和家庭废水中的微生物降解过程中作为副产品出现。对 Eurofins 从 2017 年到 2022 年的膦酸盐分析结果进行的评估表明，在 40.63% 的有机样品和 43.42% 的常规农业样品中检测到了该化合物，方法的定量限 (LOQ) 达到 0.01 mg/kg，以及超过 90% 的鹰嘴豆、小扁豆、荞麦、花生和葡萄酒的有机样品。此外，97。3% 的有机蘑菇样品含有这种化合物，用于栽培的动物粪便或堆肥是这种化学物质的潜在来源。因此，除杀菌剂应用外，食品中膦酸盐的其他原因也必须考虑在内。氧稳定同位素比值分析¹⁸ O和¹⁶ O被成功应用于有机农业矿物硫肥的检测应用。同样，它也可能是区分工业生产的膦酸盐和天然来源的膦酸盐的有前途的工具。