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It is difficult to establish a LOAEL or NOAEL for infantile methaemoglobinaemia because of difficulties in interpretation of data, as discussed earlier. Although reported data on nitrate levels in drinking water associated with methaemoglobinaemia are often inaccurate, it can be concluded that most cases of clinical infantile methaemoglobinaemia associated with the ingestion of nitrate in drinking water have occurred at levels exceeding 100 mg nitrate/L; this level is therefore considered to be the LOAEL. Although levels as low as 40 mg/L were found to be associated with elevated MeHb levels in two Hungarian studies,15 most, if not all, cases were associated with privately dug wells and quite likely involved bacterial contamination, which would greatly increase the conversion of nitrate to nitrite.
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