Table 1. Pharmaceuticals Used in the Study Dairy Farms and Theoretical Maximum Concentrations in Lagoon Water^a.

class		use g d−1		theoretical maximum concentration in lagoonb μg L−1
antibiotics	compound	Dairy I	Dairy II	Dairy I	Dairy II
aminoglycoside	dihydrostreptomycin	17.1		13
beta-lactam	amoxicillin	0.05		0.1
	ampicillin		31.3		76
	cloxacillin	0.13		0.1
	penicillin procaine G	660.0	56.0	750	135
cephalosporin	ceftiofur	14.6	10.8	16	25
	cephapirin	0.1		0.1
chloramphenicol derivative	florfenicol	2.5	1.9	2	3
lincosamide	lincomycin	6.0	5.5	8	15
	pirlimycin		0.03		0.1
macrolide	tylosin
	erythromycin
sulfonamides	sulfadimethoxine	24.3		5
	sulfamethazine	8.8	10.8	1	3
	sulfamethoxazole	8.8		3
tetracycline	oxytetracycline	7.1	2.6	8	6
	tetracycline
	chlortetracycline
other	trimethoprim	1.8		1
ionophore	lasalocid	4.1		3
	monensin	388.8	31.0	246	42
quinolone	decoquinate		7.2		17
anti-inflammatory
non steroidal	acetylsalicylic acid	445.7	369.1	68	119
	flunixin meglumine		2.1		2
steroidal	isoflupredone acetate	0.02		0.03
	dexamethasone	0.10	0.24	0.1	0.5
diuretic	furosemide	1.8	0.09	1	0.1

^aCompounds in bold were analyzed in this study. The pharmaceuticals were identified and total masses used were obtained through interviews with the dairy owners and veterinary staff, and by examining the dairy’s purchase receipts over the preceding 6- to 9-month period. The theoretical maximum is the total mass of pharmaceutical excreted divided by the lagoon volume. The details of the estimate are in the SI. Theoretical maximum concentration in lagoon = use × excretion rate × retention time/lagoon volume. Lagoon volumes are 6.66 × 10⁴ m³ (Dairy I) and 8.98 × 10⁴ m³ (Dairy II). Retention times (84.1 d (Dairy I) and 241 d (Dairy II)) are calculated using the daily water use estimate proposed by Meyer et al. (55). See SI for details on excretion rate.

^bTheoretical maximum concentrations were estimated assuming no attenuation.