Distributions of percentage methaemoglobin in several population groups in California

Several epidemiological studies in California have yielded data on percentage methaemoglobin in healthy individuals. The population groups represented include infants, elementary and high school children, and adults. The distributions of values in each group are described, as well as the differences between groups. Factors affecting the distributions are discussed. In the study of infants, the factors assessed include respiratory and gastrointestinal disease, and food and water intake. In schoolchildren, the effect of age and location of residence within Southern California are evaluated, and in adults, smoking, gender and time of day. Among infants in the 31 to 60 day age range, 33 per cent had methaemoglobin levels of 3 per cent or above, while 8 per cent had methaemoglobin levels of 4 per cent or above. Among adults, 15 per cent had levels of 3 per cent or above, while 2 per cent had levels of 4 per cent or above. Among both elementary and high school students, 3 per cent had methaemoglobin levels of 3 per cent or above, while less than 1 per cent had levels of 4 per cent or greater.