Table 4.

Assessment of risk of bias for the preclinical cell studies using the OHAT tool.

Studies	Selection Bias		Performance Bias		Detection Bias			Attrition Bias	Reporting Bias	Others
	Randomization and Concurrent Control Group	Allocation Concealment	Identical Vehicle	Blinding	Accuracy of Exposure Characterization	Consistent Exposure Administration	Blinding	Incomplete Outcome Data	Selective Outcome Reporting	Other sources of Bias
[23]	PL	NR	DL	NR	PL	DL	NR	NR	PL	PL
[24]	PL	NR	DL	NR	PL	DL	NR	NR	PL	PL
[13]	PL	NR	DL	NR	PL	DL	NR	NR	PL	PL
[25]	PL	NR	DL	NR	PL	DL	NR	NR	PL	PL
[26]	PL	NR	PL	NR	DL	DL	NR	NR	PL	PL
[27]	PL	PL	DL	DL	DL	DL	PL	NR	DL	PL
[28]	PL	NR	DL	NR	PL	DL	NR	NR	PL	PL
[29] *	PL	NR	DL	NR	PL	DL	NR	NR	PL	PL
[30]	PL	NR	PL	NR	PL	DL	NR	NR	PL	PL

DL (Definitely Low risk of bias if direct evidence of low risk-of-bias practices), PL (Probably Low risk of bias: Indirect evidence of low risk-of-bias practices OR it is deemed that deviations from low risk-of-bias practices for these criteria during the study would not appreciably bias results, including consideration of direction and magnitude of bias), PH (Probably High risk of bias: Indirect evidence of high risk-of-bias practices OR there is insufficient information “NR”) and DH (Definitely High risk of bias: Direct evidence of high risk-of-bias practices). * superscript: This study was a part of a preclinical animal study.