Antibiotics: An overview on the environmental occurrence, toxicity, degradation, and removal methods

Figures & data

Figure 1. Annual number of publications (a) and cooccurrence network map of keywords (b) about researches on the environmental occurrence, toxicity, degradation, and removal of antibiotics during the last 10 years (from 2011 to 2021)

Table 1. Concentration data of frequently detected antibiotics in different environmental compartments during 2011–2021

Antibiotics	Aquatic environment (ng/L)					Solid matrices (ng/g dry matter)		Location	Refer-ence
	Influent of WWTPs	Effluent of WWTPs	Surface water (river/estuarine)	Groundwater	Seawater (harbor)	Sediment	Sewage sludge
β-lactams
Amoxicillin	2,935–6,516 (3,746)	ND-1,129						Singapore	[11]
		ND-190 (20)	5–21 (17)					Charmoise river (France)	[19]
	200–4,600	900–1,600	ND-300			ND-43.8		Kenyan	[15]
Macrolides
Erythromycin			0.4–6.9 (3.9)			1.5–24.6 (10.2)		Huangpu river (China)	[21]
	610	160	ND-240			ND	ND	Msunduzi River (South Africa)	[29]
	111.4–403.3 (272.5)	89.8–112 (98.2)						Singapore	[11]
		ND-1,492 (395)	1–913 (293)					Charmoise river (France)	[19]
	3–470 (118)	ND-350 (129)					ND-100 (56)	Sweden	[55]
			32.3–2,910 (973)	ND-28.9 (5.63)				Jianghan Plain (Central China)	[48]
			2.50–8.16	ND-17.66		1.16–6.88		North Carolina (United States)	[49]
Roxithromycin			ND-227 (37.9)		ND-1.5 (0.38)			Bohai Sea (North China)	[44]
	25.2–65.2	7.82–58.0					ND-80	Guangdong (South China)	[16]
			0.2–2.2 (0.9)			0.3–4.1 (1.9)		Huangpu river (China)	[21]
			ND-173 (38.37)	ND-3.18 (0.088)				Jianghan Plain (Central China)	[48]
			ND-1.75 (0.44)			ND		Yangtze River (China)	[54]
Azithromycin		ND-88.0 (22.3)			ND-1.2 (0.14)			Bohai Sea (North China)	[44]
	1,537–2,951 (1,949)	367.3–980 (469.5)						Singapore	[11]
			221–2,819			ND-43.2		Leça River (Portugal)	[17]
Clarithromycin			ND-32.9 (5.0)		ND-0.82 (0.19)			Bohai Sea (North China)	[44]
	30.8–126	5.16–86					ND-69.5	Guangdong (South China)	[16]
	1,201–1,854 (1,497)	387.3–637.1 (531.7)						Singapore	[11]
			ND-32.1 (8.34)	ND-1.11 (0.02)				Jianghan Plain (Central China)	[48]
			ND-2.19 (0.26)			ND		Yangtze River (China)	[54]
			76.6–269			ND		Leça River (Portugal)	[17]
Fluoroquinolones
Ciprofloxacin			ND-346 (101)		ND-66 (31)			Bohai Sea (North China)	[44]
	15.6–90.3	5.64–9.06					296–714	Guangdong (South China)	[16]
	2,241–6,453 (3,496)	321.3–524.1 (495.5)						Singapore	[11]
		89–3,403 (817)	5–1,523 (288)			569 ± 418		Charmoise river (France)	[19]
	83–1,406 (391)	ND-62 (38)					1,600–11,000 (4,625)	Sweden	[55]
			4.46–96.0 (25.14)	0.476–26.3 (6.23)				Jianghan Plain (central China)	[48]
			ND-0.94 (0.34)			0.28–8.43 (1.24)		Yangtze River (China)	[54]
	ND-3,000	300–2,600	ND-1,300			ND-47.4		Kenyan	[15]
			ND-339			ND		Leça River (Portugal)	[17]
Ofloxacin			ND-45.4 (9.9)		ND-6.5 (0.24)			Bohai Sea (North China)	[44]
	30.3–1,010	47.4–179					1,500–5,800	Guangdong (South China)	[16]
			ND-28.5 (6.5)			ND-12.4 (4.1)		Huangpu river (China)	[21]
		805–8,637 (4,312)	100–2,888 (1,209)			498 ± 261		Charmoise river (France)	[19]
			ND-45.3 (9.03)	ND-7.2 (0.47)				Jianghan Plain (Central China)	[48]
			ND-0.82 (0.32)			0.29–84.17 (44.27)		Yangtze River (China)	[54]
			ND-120			ND		Leça River (Portugal)	[17]
Norfloxacin			ND-572 (118)		7.5–103 (40)			Bohai Sea (North China)	[44]
	42.4–974	36.7–61					1,820–5,610	Guangdong (South China)	[16]
		97–9,347 (1,542)	14–1,261 (289)			225 ± 70		Charmoise river (France)	[19]
			9.57–277 (65.87)	1.19–142 (23.75)				Jianghan Plain (Central China)	[48]
			ND-0.83 (0.32)			0.15–0.83 (0.4)		Yangtze River (China)	[54]
	900–2,800	500–2,900	ND-2,200			ND-26.6		Kenyan	[15]
Enrofloxacin			ND-24.6 (10.6)		ND-7.6 (1.8)			Bohai Sea (North China)	[44]
			ND-14.6 (2.8)			ND-8.9 (3.2)		Huangpu river (China)	[21]
		ND-636 (57)	ND			11 ± 4.1		Charmoise river (France)	[19]
			ND-136 (35.56)	ND-30.3 (7.20)				Jianghan Plain (Central China)	[48]
			ND-0.89 (0.4)			0.31–0.95 (0.58)		Yangtze River (China)	[54]
Enoxacin			ND-508 (116)		ND-209 (62)			Bohai Sea (North China)	[44]
		ND-1,634 (169)	ND-1,310 (134)			31 ± 18		Charmoise river (France)	[19]
Lomefloxacin	3.22–25.5	ND-8.59					25.1–440	Guangdong (South China)	[16]
		ND-16 (3)	3.6–6.7 (5.5)			5.3 ± 4.9		Charmoise river (France)	[19]
			ND-36.4 (9.98)	ND-10.7 (2.11)				Jianghan Plain (Central China)	[48]
Tetracyclines
Tetracycline	40.1–316	7.73–35.1					353–1,650	Guangdong (South China)	[16]
			ND-54.3 (4.2)			ND-21.7 (3.5)		Huangpu river (China)	[21]
	1,240–12,340 (3,604)	691.2–1,536 (766.4)						Singapore	[11]
		ND-238 (47)	ND-68 (16)					Charmoise river (France)	[19]
			ND-122 (36.25)	ND-38.9 (4.78)				Jianghan Plain (Central China)	[48]
Chlortetracycline	7.46–35.7	ND					34.6–455	Guangdong (South China)	[16]
			ND-46.7 (3.6)			ND-6.3 (2.4)		Huangpu river (China)	[21]
	2,333–15,911 (6,434)	1,472–1,986 (1,757)						Singapore	[11]
			12.3–109 (33)	0.71–59.6 (6.16)				Jianghan Plain, (Central China)	[48]
			ND-0.95 (0.55)			ND-0.95 (0.39)		Yangtze River (China)	[54]
Oxytetracycline	79.1–560	10.8–17.6					417–1,680	Guangdong (South China)	[16]
			ND-219.8 (78.3)			0.6–18.6 (6.9)		Huangpu river (China)	[21]
	1,629–30,049 (4,887)	839.8–2,014 (1,469)						Singapore	[11]
			ND-63.1(24.79)	ND-24.3 (3.18)				Jianghan Plain (Central China)	[48]
			ND-0.97 (0.37)			0.16–0.93 (0.41)		Yangtze River (China)	[54]
Doxycycline	ND-23.0	ND					103–232	Guangdong (South China)	[16]
			ND-112.3 (11.3)			ND-21.3 (7.0)		Huangpu river (China)	[21]
	ND-2,700	400–1,500	ND-700			ND-32.2		Kenyan	[15]
Minocycline	730.9–3,808 (1,233)	ND						Singapore	[11]
Sulfonamides
Sulfamethoxazole			0.36–527 (62.8)		1.5–82 (19)			Bohai Sea (North China)	[44]
	216–239	65.2–106					ND-10.0	Guangdong (South China)	[16]
			2.2–764.9 (259.6)			0.05–0.6 (0.2)		Huangpu river (China)	[21]
	34,500	ND	ND-5,320			ND	ND	Msunduzi River (South Africa)	[29]
	893.4–1,389 (1,172)	301.5–463.4 (311.3)						Singapore	[11]
		407–12,848 (3,375)	41–3,066 (1,119)			7.2 ± 2.1		Charmoise river (France)	[19]
			1.92–30.2 (13.67)	ND-7.29 (1.01)				Jianghan Plain (Central China)	[48]
		374.3–1,309.5 (842.4)	15–218 (130)	47.8–251.4 (106)				Bolivia	[47]
			0.43–7.95 (3.84)			0.14–2.04 (1.39)		Yangtze River (China)	[54]
			5.97–14.54	1.01–54.04		2.77–6.89		North Carolina (United States)	[49]
Sulfadiazine			ND-18.7 (1.7)		ND-0.43 (0.02)			Bohai Sea (North China)	[44]
	15.2–40.1	1.14–9.67					ND	Guangdong (South China)	[16]
			4.9–112.5 (53.6)			0.07–0.71 (0.4)		Huangpu river (China)	[21]
			ND-16.7 (5.16)	ND-2.87 (0.55)				Jianghan Plain (Central China)	[48]
			ND-0.46 (0.23)			ND-0.57 (0.1)		Yangtze River (China)	[54]
Sulfamethazine	12.8–131	7.3–23.3					ND-3.83	Guangdong (South China)	[16]
			19.9–389.4 (188.9)			0.2–2.7 (1.2)		Huangpu river (China)	[21]
	ND	ND	ND-1,090			ND	ND	Msunduzi River (South Africa)	[29]
	449.9–1,814 (802.8)	73–260.8 (135.9)						Singapore	[11]
			ND-27.3 (5.36)	ND-15.9 (0.50)				Jianghan Plain (Central China)	[48]
			0.24–0.79 (0.48)			ND-0.27 (0.16)		Yangtze River (China)	[54]
Sulfapyridine	29.8–121	7.08–24.1					ND-2.31	Guangdong (South China)	[16]
			ND-103.1 (24.1)			ND-6.6 (1.7)		Huangpu river (China)	[21]
Diaminopyrimidines
Trimethoprim			ND-13,600 (1,133)		1.3–330 (53)			Bohai Sea (North China)	[44]
	72.3–162	31.1–64					3.57–10.7	Guangdong (South China)	[16]
	ND	ND	ND-290			ND- 87.55	ND	Msunduzi River (South Africa)	[29]
	197.6–251.2 (235.5)	124.9–178.6 (151.6)						Singapore	[11]
		ND-5,316 (1,568)	1–1,573 (442)			52 ± 27		Charmoise river (France)	[19]
	51–340 (115)	10–130 (61)					ND-58 (42)	Sweden	[55]
		271–336.5 (304)	46–312 (159)	108–200.2 (154.2)				Bolivia	[47]
			0.24–0.96 (0.73)			ND-0.99 (0.23)		Yangtze River (China)	[54]
	100–5,600	100–500	ND-200			ND-13.3		Kenyan	[15]
			ND-110			ND		Leça River (Portugal)	[17]
Degradation products
AMX penilloic acid		150		30				Israel	[133]
AMX 2ʹ,5ʹ- diketopiperazine		500						Israel
Erythromycin -H2O	771–942	83.9–695					29.3–147	Guangdong (South China)	[16]
	299.3–737 (652.1)	194.5–381 (272.6)						Singapore	[11]
			ND-30 (4.67)			ND-6.78 (1.2)		Yangtze River (China)	[54]
D-ciprofloxacin		ND-127 (27)	7–71 (16)			22 ± 11		Charmoise river (France)	[19]
4-epidemeclocycline			17–1,159					Canada	[20]
Isochlortetracycline			192–3,256					Canada
N-acetyl SMX		18–1,245 (410)	4–406 (124)					Charmoise river (France)	[19]
			ND-290.3	ND				Bolivia	[47]
SMX-N1-glucuronide			ND-233.7	ND				Bolivia

Note: WWTPs: wastewater treatment plants; max: maximum concentration; med: median concentration; A-B (C): range (mean/median); (A ± B): (mean±SD); ND: no detected or below detection limit; AMX: amoxicillin; SMX: sulfamethoxazole; D-ciprofloxacin: desethylene ciprofloxacin

Figure 2. Top twenty active countries that conducted researches on the occurrence of antibiotics in the environment, and corresponding annual number of publications from 2011 to 2021

Table 2. Toxicity data of antibiotics to non-target aquatic organisms

Antibiotics	Taxonomic group	Species	Endpoint	Value (mg/L)	Reference
β-lactams
Amoxicillin	Cyanobacteria	Anabaena CPB4337	72 h-EC50 (bioluminescence)	56.3	[64]
	Algae	P. subcapitata	72 h-EC50 (growth)	>1500
			72 h-EC50 (growth)	>2000	[86]
Ampicillin	Algae	P. subcapitata	72 h-EC50 (growth)	>2000
Cephalothin	Algae	P. subcapitata	72 h-EC50 (growth)	>600
Macrolides
Erythromycin	Cyanobacteria	Anabaena CPB4337	72 h-EC50 (bioluminescence)	0.022	[64]
	Algae	P. subcapitata	72 h-EC50 (growth)	0.35
Tylosin	Cyanobacteria	A. flos-aquae	4d-EC50 (growth)	0.098	[83]
		S. leopoliensis	4d-EC50 (growth)	0.096
	Algae	P. subcapitata	4d-EC50 (growth)	4.41
		D. subspicatus	4d-EC50 (growth)	13
		Chlorella vulgaris	4d-EC50 (growth)	>86.57
		Navicula pelliculosa	4d-EC50 (growth)	1.41
		P. tricornutum	4d-EC50 (growth)	6.08
		C. closterium	(4–5d) IC50 (growth)	0.27	[85]
		N. ramosissima	(4–5d) IC50 (growth)	0.99
Clarithromycin	Cyanobacteria	A. flos-aquae	72 h-EC50 (growth)	0.0121	[71]
	Algae	D. subspicatus	72 h-EC50 (growth)	0.0371
			72 h-NOEC	0.025
	Duckweed	lemna minor	7d-EC50 (growth)	>1.9
			7d-EC50 (growth)	0.8
	Crustaceans	Daphnia magna	48 h-EC50 (immobilization)	>2
			21d-NOEC (reproduction)	>2.1
	Fish	Danio rerio (embryo)	48 h-EC50 (lethality)	>2
Fluoroquinolones
Ciprofloxacin	Marine bacteria	periphytic bacteria	72 h-EC50 (growth)	0.16	[182]
			72 h-NOEC (growth)	0.0086
			72 h-EC50 (growth)	11.3	[86]
	Algae	C. closterium	(4–5d) IC50 (growth)	55.43	[85]
		N. ramosissima	(4–5d) IC50 (growth)	72.12
		Chlorella vulgaris	72 h-IC50 (growth)	9.23	[87]
			96 h-IC50 (growth)	29.09
			72 h-NOEC (growth)	<20
			72-LOEC (growth)	20
		C. mexicana	96 h-EC50 (growth)	65	[74]
Levofloxacin	Cyanobacteria	Anabaena CPB4337	72 h-EC50 (bioluminescence)	4.8	[64]
	Algae	P. subcapitata	72 h-EC50 (growth)	>120
Norfloxacin	Cyanobacteria	Anabaena CPB4337	72 h-EC50 (bioluminescence)	5.6
	Algae	P. subcapitata	72 h-EC50 (growth)	>80
Tetracyclines
Tetracycline	Cyanobacteria	Anabaena CPB4337	72 h-EC50 (bioluminescence)	6.2	[64]
	Algae	P. subcapitata	72 h-EC50 (growth)	3.31
	Ciliates	Stentor coeruleus	24 h-EC50 (growth)	94.4	[69]
		Stylonychia lemnae	24 h-EC50 (growth)	40.1
Oxytetracycline	Algae	Tetraselmis suecica	96 h-IC50 (growth)	17.25	[32]
Sulfonamides
Sulfamonomethoxine	Algae	Chlorella vulgaris	72 h-EC50 (growth)	5.9	[65]
		Isochrysis galbana	72 h-EC50 (growth)	9.7	[65]
	Crustaceans	Daphnia magna	48 h-LC50 (survival)	48
			21d-EC50 (reproduction)	14.9
		Daphnia similis	48 h-LC50 (survival)	283
			21d-EC50 (reproduction)	41.9
	Fish	Oryzias latipes	96 h-LC50 (survival)	>1000
Sulfamethazine	Marine bacteria	Vibrio fischeri	30 min-EC50	>100	[67]
		A. globiformis	4h-EC50	>139
	Algae	S. vacuolatus	24 h-EC50 (growth)	19.52
	Duckweed	Lemna minor	7d-EC50 (growth)	1.74
Sulfadiazine	Marine bacteria	Vibrio fischeri	30 min-EC50	>25
		A. globiformis	4h-EC50	>125
	Algae	S. vacuolatus	24 h-EC50 (growth)	2.22
	Duckweed	Lemna minor	7d-EC50 (growth)	0.07
Sulfamerazine	Marine bacteria	Vibrio fischeri	30 min-EC50	>50
		A. globiformis	4 h-EC50	>132
	Algae	S. vacuolatus	24 h-EC50 (growth)	11.90
	Duckweed	Lemna minor	7d-EC50 (growth)	0.68
Sulfamethoxazole	Marine bacteria	Vibrio fischeri	30 min-EC50	>100
		periphytic bacteria	72 h-EC50 (growth)	0.27	[182]
	Algae	S. vacuolatus	24 h-EC50 (growth)	1.54	[67]
	Duckweed	Lemna minor	7d-EC50 (growth)	0.21
Sulfathiazole	Marine bacteria	Vibrio fischeri	30 min-EC50	>50
	Algae	S. vacuolatus	24 h-EC50 (growth)	13.10
	Duckweed	Lemna minor	7d-EC50 (growth)	4.89
Sulfapyridine	Marine bacteria	Vibrio fischeri	30 min-EC50	>50
	Algae	S. vacuolatus	24 h-EC50 (growth)	5.28
	Duckweed	Lemna minor	7d-EC50 (growth)	0.46
Sulfamethoxypyridazine	Marine bacteria	Vibrio fischeri	30 min-EC50	>100
	Algae	S. vacuolatus	24 h-EC50 (growth)	3.82
	Duckweed	Lemna minor	7d-EC50 (growth)	1.51
Diaminopyrimidines
Trimethoprim	Cyanobacteria	A. flos-aquae	4d-EC50 (growth)	91.68	[83]
		S. leopoliensis	4d-EC50 (growth)	>100
	Algae	P. subcapitata	4d-EC50 (growth)	>63.37
		D. subspicatus	4d-EC50 (growth)	>100
		Chlorella vulgaris	4d-EC50 (growth)	>100
		Navicula pelliculosa	4d-EC50 (growth)	2.14
		P. tricornutum	4d-EC50 (growth)	21.66
Others
Lincomycin	Cyanobacteria	A. flos-aquae	4d-EC50 (growth)	0.058	[83]
		S. leopoliensis	4d-EC50 (growth)	0.042
	Algae	P. subcapitata	4d-EC50 (growth)	3.26
		D. subspicatus	4d-EC50 (growth)	7.12
		Chlorella vulgaris	4d-EC50 (growth)	>100
		Navicula pelliculosa	4d-EC50 (growth)	>100
		P. tricornutum	4d-EC50 (growth)	>100
		C. closterium	(4–5d) IC50 (growth)	14.16	[85]
		N. ramosissima	(4–5d) IC50 (growth)	11.08
Chloramphenicol	Algae	Tetraselmis suecica	96 h-IC50 (growth)	11.16	[32]
Florphenicol	Algae	Tetraselmis suecica	96 h-IC50 (growth)	9.03
Gentamycin	Algae	P. subcapitata	72 h-EC50 (growth)	19.2	[86]
Vancomycin	Algae	P. subcapitata	72 h-EC50 (growth)	724
14-hydroxy (R)-clarithromycin	Cyanobacteria	A. flos-aquae	72 h-EC50 (growth)	0.0272	[71]
			72 h-NOEC	0.0027
	Algae	D. subspicatus	72 h-EC50 (growth)	0.0463
			72 h-NOEC	0.02
	Crustaceans	Daphnia magna	48 h-EC50 (immobilization)	>2
			21d-NOEC (reproduction)	>0.85
	Fish	Danio rerio (embryo)	48 h-EC50 (lethality)	>2
N-desmethyl- clarithromycin	Cyanobacteria	A. flos-aquae	72 h-EC50 (growth)	0.134
	Algae	D. subspicatus	72 h-EC50 (growth)	0.575
			72 h-NOEC	0.115
	Crustaceans	Daphnia magna	48 h-EC50 (immobilization)	>0.7
			21d-NOEC (reproduction)	0.15
			21d-LOEC (reproduction)	0.75
	Fish	Danio rerio (embryo)	48 h-EC50 (lethality)	>2

Note: Pseudokirchneriella subcapitata: P. subcapitata; Anabaena flos-aquae: A. flos-aquae; Synechococcus leopoliensis: S. leopoliensis; Cylindrotheca closterium: C. closterium; Navicula ramosissima: N. ramosissima; Desmodesmus subspicatus: D. subspicatus; Phaeodactylum tricornutum: P. tricornutum; Microcystis aeruginosa: M. aeruginosa; Chlamydomonas mexicana: C. mexicana; Arthrobacter globiformis: A. globiformis; Scenedesmus vacuolatus: S. vacuolatus; EC50: median effective concentration; LC50: median lethal concentration; IC50: median inhibition concentration; NOEC: no-observed-effect concentration; LOEC: lowest observed effect concentration

Table 3. Identified transformation of antibiotics

Category	Parent compound	Degradation method	Intermediate/product (structural formula)	(m/z)/[M + H]^+	Proposed structure	Product name	Reaction mechanism	Reference
				Experimental
β-lactams	Amoxicillin	Hydrolysis (pH 2/7/8/10)	C15H22N3O4S	340.1316	*	(5 R)-AMX penilloic acid *	β-lactam ring cleavage, decarboxylation	[132]
			C15H22N3O4S	340.1337	*	(5S)-AMX penilloic acid *	epimerization
			C16H20N3O5S	366.1131	*	(5 R)-AMX 2ʹ, 5ʹ- diketopiperazine*	β-lactam ring cleavage, decarboxylation, internal rearrangement
			C16H20N3O5S	366.1124	*	(5S)-AMX 2ʹ, 5ʹ- diketopiperazine*	epimerization
			C17H24N3O6S	398.1383		amoxicilloic acid methyl ester	β-lactam ring cleavage
		Hydrolysis (pH 5/7/8)		189	*	phenol hydroxypyrazine*	a series of AMX-degradation processes	[133]
				384	*	AMX penicilloic acid *
	Ampicillin	Hydrolysis (pH4 & 60°C)		173.1			amide cleavage, ecarboxylation	[135]
				410.1			β-lactam cleavage
		Hydrolysis (pH7/9 & 60°C)		368.1			β-lactam cleavage
				368.1			β-lactam cleavage, pimerization
				324.1			β-lactam cleavage, decarboxylation
	Cefalotin	Hydrolysis (pH4 & 60°C)		311.1			ester hydrolysis, decarboxylation	[135]
				333.1			β-lactam cleavage, ester hydrolysis, decarboxylation
		Hydrolysis (pH 7/9 &60°C)		247.0			β-lactam hydration, ester and amide hydrolysis
		Hydrolysis (pH 4/7/9 & 60°C)		377.1			β-lactam hydration, ester hydrolysis
				238.1			β-lactam hydration, acetate hydrolysis, C-N side chain cleavage
				224.1			β-lactam hydration, acetate hydrolysis, C-N side chain cleavage
	Cefoxitin	Hydrolysis (pH4/7 & 60°C)		407.0			carbamate hydrolysis	[135]
				297.0			side chain cleavage, decarboxylation
				389.0			carbamate hydrolysis, β-lactam hydration
		Hydrolysis (pH7/9 & 60°C)		221.1			β-lactam cleavage, carbamate and amide hydrolysis
				251.1			β-lactam hydration, carbamate and amide hydrolysis
		Hydrolysis (pH4/7/9 & 60°C)		268.1			β-lactam hydration, carbamate hydrolysis, C-N side chain cleavage
				254.1			demethylation
				236.1			side chain cleavage
	Cephradine	Photolysis (Simulated sunlight)		306			decarboxylation	[51]
				211			β-lactam cleavage
	Cephalexin	Photolysis (Simulated sunlight)		304			decarboxylation	[51]
				209			β-lactam cleavage
	Cephapirin	Photolysis (Simulated sunlight)		126				[51]
				380			decarboxylation
Macrolides	Clarithromycin	Biodegradation (T. harzianum and Pleurotus ostreatus)	C38H70NO14	764.48		14-hydroxy-CTM	hydroxylation	[176]
			C37H68NO13	734.47		N-desmethyl-CTM	desmethyl
			C30H56NO11	606.38		14-hydroxy-descladinosyl-CTM	cleavage of the glycosidic bond, L-cladinose moiety loss
			C30H56NO10	590.39		descladinosyl-CTM	cleavage of the glycosidic bond, L-cladinose moiety loss
	Erythromycin	UV photolysis (254 nm)	C34H64NO12	678.4429			cladinose ring cleavage	[152]
			C29H54NO12	608.3647			cladinose ring cleavage
			C29H52NO11	590.3542			cladinose ring cleavage
			C23H41O7	429.2825			formate adduct
		Biodegradation (Ochrobactrum sp. strain)		575.37		3-depyranosyloxy erythromycin	depyranosyloxy	[175]
				418.26		7,12-dyhydroxy-6-deoxyerythronolide
				386.27		6-deoxyerythronolide
				75.04			propionaldehyde
	Roxithromycin	UV photolysis (254 nm)	C37H68NO13	734.4691		erythromycin		[152]
			C29H54NO10	576.3748			cladinose moiety loss
	Tylosin	Hydrolysis (pH9 & 60°C)		936.6			cyclic ester hydrolysis, alcohol formation	[136]
				934.5			cyclic ester hydrolysis
				916.5			tylosin isomer
		Hydrolysis (pH4 & 60°C)		772.4			mycarose loss
	Spiramycin	Hydrolysis (pH7/9 & 60°C)		861.5			cyclic ester hydrolysis	[136]
		Hydrolysis (pH4 & 60°C)		699.4			mycarose sugar loss
				558.3			mycarose and forosamine loss
Fluoroquinolones	Enrofloxacin	Photolysis (pH 7–8 & Simulated sunlight)	C19H23N3O4	358.1769			hydroxyl group substitutes F atom	[139]
			C17H21N3O3	316.1660			defluorination, piperazine ring cleavage
			C17H18FN3O3	332.1415		ciprofloxacin	desethyl
			C19H23N3O5	374.1713			hydroxylation
	Ciprofloxacin	Photolysis		330		1-cyclopropyl-6-hydroxy-4-oxo-7-(piperazin-1-yl)-1,4-dihydroquinoline-3- carboxyl acid	hydroxyl group substitutes F atom	[141]
				346		1-cyclopropyl-2,6-dihydroxy-4-oxo-7-(piperazin–yl) 1,4-dihydroquin oline-3-carboxyl acid	di-hydroxylation
				316		7-[(2-ethylamino)(formyl)amino]-1-cyclopropyl-4-oxo-1,4-dihydroquinoline-3- carboxyl acid	defluorination, piperazine ring cleavage
				288		1-cyclopropyl-6-fluoro-7- (piperazin-1-yl) quinolin- 4(1H)-one	decarboxylation
		UV photolysis (254 nm)	C17H19FN3O4	348.1354			mono-hydroxylation	[152]
			C17H20FN3O5	346.1394			di-hydroxylation
			C17H20FN3O4	330.1444			hydroxyl group substitutes F atom
			C16H18FN3O4	316.1287			piperazinyl ring cleavage
			C15H18FN3O2	272.1391			piperazinyl ring cleavage, decarboxylation
			C15H18FN3O3	288.134
			C17H20FN3O3	314.1499			defluorination
			C13H13FN2O3	245.0917			piperazinyl ring cleavage
		Biodegradation (mixture of F11, FP1 and S2)	C13H12FN2O3	262.90			piperazine ring cleavage	[165]
			C15H17FN3O3	305.93			C2H2 loss
			C17H19FN3O4	347.90			hydroxylation
	Norfloxacin	UV Photolysis (pH 2–12)	C16H12FN2O7	363.0631			oxidation	[137]
			C14H17FN3O3	294.1237			piperazine ring cleavage
			C14H16FN2O3	279.1132
			C12H12FN2O3	251.0827
			C16H15FN3O5	348.1013			oxidation
		Biodegradation (mixture of F11, FP1 and S2)	C16H19FN3O4	335.90			piperazinyl ring cleavage	[165]
			C14H17FN3O3	293.93			piperazinyl ring cleavage (C2H2 loss)
			C16H20N3O4	317.93			piperazine ring cleavage, amide formation, defluorination
	Ofloxacin	Sorption on TiO2 surfaces		227.0			piperazinyl ring loss, demethylation	[183]
				242.9			piperazinyl ring loss, decarboxylation, hydroxylation
				259.0			piperazinyl ring loss, decarboxylation, hydroxylation
		Desorption from TiO2 surfaces		159.0
				319.9			demethylation
				348.1			demethylation
		Biodegradation (mixture of F11, FP1 and S2)	C17H19FN3O4	348.00			demethylation	[165]
			C16H19FN3O4	336.10			decarboxylation, hydroxylation
	Moxifloxacin	Biodegradation (mixture of F11, FP1 and S2)	C14H14FN2O4	292.90			(4aS,7aS)-octahydro-6 H- pyrrolo [3,4-b] pyridine-6-yl group oxidation	[165]
			C21H23FN3O5	415.92
Tetracyclines	Oxytetracycline	UV-visible light photolysis		416.5		analogue of 4-dedimethylaminotetrcycline (DTC)	dedimethylamino	[138]
	Chlortetracycline	Biodegradation (Firmicutes, Proteobacteria and Bacteroidetes	C18H20O6	332.1			Cl atom loss, -N(CH3)2 loss	[177]
			C22H23N2O8	445.1		tetracycline	Cl atom loss
			C21H21ClN2O8	465.0		6-demethyl- chlortetracycline	methyl group loss from the -N(CH3)2
				511			di-hydroxylation
Sulfonamides	Sulfadiazine	Biodegradation (Arthrobacter spp)		96	*	2-Aminopyrimidine*		[171]
				112	*	2-amino-4- hydroxypyrimidine *	hydroxylation
				128	*	2-amino-4, 6-dihydroxypyrimidine*	di-hydroxylation
				173	*	Sulfanilamide*
				87
				176			pyrimidin-2ylsulfamic acid
							aniline acetylation
	Sulfanilamide	Biodegradation		108.1			p-phenylenediamine	[180]
				155.8			benzene sulfonamide
				190.4			hydroxylamine benzene sulfonamide
	Sulfamethoxazole	UV photolysis (350 nm)	C10H14N3O	192.1131			sulfur dioxide loss	[152]
		Biodegradation	C12H13N3O4S	294.0554	*	N4-acetyl -SMX*	acetylation	[184]
			C12H13N3O4S	296.0696		N1-acetyl – SMX	acetylation
	Trimethoprim	Biodegradation	C14H18N4O4	307.1399			hydroxylation	[184]
	Sulfamethoxypyridazine	UV photolysis	C11H12N4O4S	297.1			hydroxylation	[151]
			C11H11N4O4S	295.1			N-oxidation
Others	Chloramphenicol	Hydrolysis (pH4/7/9 & 60°C)		213.1			amide hydrolysis	[136]
	Florfenicol	Hydrolysis (pH4/7/9 & 60°C)		356.0			alkyl fluorine hydrolysis	[136]
		Hydrolysis (pH7 & 60°C)		288.1			dechlorination and alkyl fluorine hydrolysis
		Hydrolysis (pH4 & 60°C)		248.1			amide hydrolysis
		Hydrolysis (pH7/9 & 60°C)		272.1			alkyl fluorine hydrolysis, dechlorination, demethylation
				246.1			Amide and alkyl fluorine hydrolysis
	Clindamycine	Biodegradation	C18H33ClN2O6S	441.1817			clindamycin sulfoxide	[184]
			C18H33ClN2O7S	457.1784			Hydroxy clindamycin sulfoxide
			C17H31ClN2O5S	411.1713			S-demethyl clindamycin
			C17H31ClN2O5S	411.1720			N-demethyl clindamycin

*Indicates exact structure.

Figure 3. Proposed degradation pathways for SMX and its metabolites. (a) Under simulated solar (source [148]:); (b) under UV/CoFe₂O₄/TiO₂ (source [150]:)

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