Contamination measured for worktop before cleaning process.

Results for contamination rates are presented as number of positive samples/number of measured samples (n/N) and in %. Drug amounts are expressed in ng/cm2. Drugs are classified according to the frequency of positive samples in the Standard group.污染率的结果以阳性样本数/检测样本数（n/N）以及百分比（%）两种形式呈现。药物含量以纳克每平方厘米（ng/cm²）为单位表示。药物将根据标准组中的阳性样本出现频率进行分类。