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Health risks of cyanuric acid
Cyanuric acid is a by-product of the process of adding disinfectants to swimming pool water.

Considering the adverse effects of cyanuric acid on human health, the U.S. Environmental Protection Agency has classified cyanuric acid as one of the drinking water pollutants. The potential health risks associated with cyanuric acid stem from its ability to inhibit the efficiency of chlorine in disinfection. The excessive levels of cyanuric acid reduce chlorine activity, facilitating microbial proliferation in pool water. This compromised disinfection may increase the risk of waterborne illnesses due to inadequate elimination of bacteria, viruses, and other pathogens. Irrespective of ingestion or skin contact, direct exposure to high concentrations of cyanuric acid can lead to irritation, gastrointestinal distress, and in extreme cases, severe health effects.

In addition, when cyanuric acid and melamine are simultaneously present in the swimming pool water, the toxicity increases compared to cyanuric acid alone. This phenomenon may have an adverse effect on the urinary system of the human body, causing kidney and bladder stones and leading to kidney failure in severe cases (19). Occasionally, melamine is detected in the swimming pool water due to various factors, primarily related to its use in pool-related products or accidental contamination, especially in less regulated regions where it might be utilized in pool construction or maintenance (10). Several studies have highlighted the presence of melamine in food and its association with kidney toxicity, especially in cases of co-exposure to cyanuric acid and phthalates, emphasizing the risk of early kidney impairment. Dorne et al. (20) and Liu et al. (21) examined the interactions between these compounds and their effects on kidney health. The mechanism of melamine toxicity involves the formation of crystals with cyanuric acid in renal tubules, potentially leading to acute kidney failure. The co-exposure of cyanuric acid and melamine in animals and humans exhibited increased toxicity compared to individual exposure. Moreover, Xu et al. (22) underscored the complex toxic effects arising from co-exposure to melamine and cyanuric acid, showing cytotoxic and genotoxic effects in human kidney cells, which in turn suggested the formation of melamine-cyanuric acid complex.

Furthermore, cyanuric acid is implicated in pathological changes in other organs, including the spleen (23), liver (24), uterus (25), and humoral immune function (26). A recent study demonstrated that cyanuric acid inhibits presynaptic neurotransmission in a dose-dependent manner by suppressing the frequency of excitatory postsynaptic currents in the hippocampal slices (27). This phenomenon might be attributed to changes in residual calcium concentration at presynaptic terminals, as demonstrated by enhanced paired pulses (27). Interestingly, exposure to 10, 20, and 40 mg/kg cyanuric acid for four weeks severely damages thyroid hormone homeostasis, leading to anxiety-and depression-like behaviors (28). Therefore, it can be deduced that high concentrations of cyanuric acid induce neurotoxicity in various products (29). Melamine and cyanuric acid exhibited low toxicity individually but high toxicological effects upon co-exposure. Also, co-exposure leads to significant oxidative stress and damage to placental development, resulting in increased apoptosis and decreased fetal cell proliferation (30). The co-exposure severely impairs neuronal and synaptic functions, reducing the amplitude, decay time, and frequency of miniature excitatory postsynaptic currents (mEPSCs) without affecting miniature inhibitory postsynaptic currents (mIPSCs) (31). Prenatal exposure to cyanuric acid elevates alkaline phosphatase levels in the maternal placenta and fetal brains (32).

https://www.frontiersin.org/journals/public-health/articles/10.3389/fpubh.2023.1294842/full