Abstract
Consumption of cow's milk, which is associated with diet and health benefits, has decreased in the USA. The simultaneous increase in demand for more costly organic milk suggests consumer concern about exposure to production-related contaminants may be contributing to this decline. We sought to determine if contaminant levels differ by the production method used. Half-gallon containers of organic and conventional milk (four each) were collected by volunteers in each of nine US regions and shipped on ice for analysis. Pesticide, antibiotic and hormone (bovine growth hormone (bGH), bGH-associated insulin-like growth factor 1 (IGF-1)) residues were measured using liquid or gas chromatography coupled to mass or tandem mass spectrometry. Levels were compared against established federal limits and by production method. Laboratory analysis of retail milk samples. Current-use pesticides (5/15 tested) and antibiotics (5/13 tested) were detected in several conventional (26-60 %; n 35) but not in organic (n 34) samples. Among the conventional samples, residue levels exceeded federal limits for amoxicillin in one sample (3 %) and in multiple samples for sulfamethazine (37 %) and sulfathiazole (26 %). Median bGH and IGF-1 concentrations in conventional milk were 9·8 and 3·5 ng/ml, respectively, twenty and three times that in organic samples (P < 0·0001). Current-use antibiotics and pesticides were undetectable in organic but prevalent in conventionally produced milk samples, with multiple samples exceeding federal limits. Higher bGH and IGF-1 levels in conventional milk suggest the presence of synthetic growth hormone. Further research is needed to understand the impact of these differences, if any, on consumers.
Highlights
From one region (New York) only two of the three requested samples of 2 % conventional milk were available for analysis and from another (Rocky Mountain) only one of the three requested samples of 2 % organic milk were
The adjusted least-squares mean for Bovine growth hormone (bGH) was 9·4 (8·2, 10·7) ng/ml and for insulin-like growth factor 1 (IGF-1) it was 3·9 (3·1, 4·6) ng/ml and both still differed significantly from their organic counterparts (P < 0·0001). These results demonstrate that antibiotics and current-use pesticides were prevalent in the conventionally produced but not the organically produced milk samples collected from retail sites across the USA
We found that the levels of bGH and IGF-1 in conventional milk were significantly greater than those in the samples produced organically
Summary
Sample collection Milk samples were collected in August 2015 from each of nine regions dividing the continental USA. Regional boundaries were those specified on a map made publicly Northwest Rocky Mountain Midwest California Southwest. Northeast New York Great Lakes Northeast Southeast.
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