Low exposure to melamine increases the risk of urolithiasis in adults

Abstract

Melamine, a widely used chemical found in many products in daily use, became a public health concern due to melamine-associated urinary stone formation in children. In adults, it is still unknown whether low-dose melamine exposure may also cause urolithiasis. To address this question, we studied 211 Taiwanese patients diagnosed with calcium urolithiasis and 211 age- and gender-matched controls. All patients completed a detailed questionnaire and provided blood and urine samples for biochemical analysis. Urinary melamine concentrations were measured by triple-quadrupole liquid chromatography tandem mass spectrometry. Compared with those whose urinary melamine levels were below the detection limit of the method, patients with urinary melamine levels of up to 3.11 ng/ml and those with levels of ≥3.12 ng/ml had 3.01- and 7.64-fold increased risk, respectively, of calcium urolithiasis after adjusting for educational level, fluid intake, cigarette smoking, betel quid chewing, alcohol drinking, urinary uric acid, calcium, creatinine, and estimated creatinine clearance rate. The population attributable risk of calcium urolithiasis averaged 50% when melamine was detected in the urine, after considering other covariates. MALDI-TOF mass spectrometry detected melamine in the stones of nine representative patients who had measurable urinary melamine levels. Thus, low-dose melamine exposure can play an important role in calcium urolithiasis in Taiwanese adults.

Development of analytical method of melamine in placenta from pregnant women by isotope‐dilution liquid chromatography/tandem mass spectrometry

“…For the assessment of direct fetal exposure to various substances during pregnancy, measurements of biomarkers in placental, amniotic fluid or breast milk may be more appropriate than in urine or blood on potential health effects, in the case of our study, daily‐life exposure to melamine. Observational studies, mostly ours, have linked exposure to melamine in the environment to early renal injury in humans . No human studies have attempted to examine the effect of maternal melamine exposure on kidney function or renal morphology in their fetuses; only animal studies have investigated this relationship .…”

“…Several kinds of tableware are also made of melamine, which can migrate into food when that tableware comes into contact with high temperatures or acid . Several research groups studying long‐term low‐dose melamine exposure have suggested that melamine‐induced oxidative stress and inflammation play pathological roles in renal injury . Epidemiological studies have also associated melamine exposure and early renal injury markers in children and occupational workers …”

Ambient Melamine Exposure and Urinary Biomarkers of Early Renal Injury

“…For covariates in the model, we first included the variable of serum uric acid, because it was the most important risk factor of urolithiasis in previous studies, including ours. 30,31 Then, other covariates were added to models in a forward stepwise selection and were finally included if they altered the association between melamine exposure and risk of renal injury indicators by greater than 10%. The additional covariates included age, sex, education, body mass index, smoking status, and serum uric acid.…”

The effects of environmental chemicals on renal function

“…6,9 The long-term consequences of melamine exposure in infancy and early childhood remain unknown, 10 but exposure to melamine during adulthood might increase the risk of urolithiasis. 11 The melamine story, therefore, provides a striking cautionary note regarding the potential serious adverse consequences of exposure to environmental organic chemicals during normal consumer activity.…”