This quasi-experimental study found significant improvement in the KAP scores post compared to pre-intervention. The post-knowledge and attitude scores were significantly better in nurses and participants with a higher education. The post-practice scores were significantly better for females, participants with an age ≥ 30 years, higher education, and nursing jobs.

4.1 Knowledge scores

The current study results revealed that knowledge scores were significantly higher after the intervention. These results agree with El-Naggar et al. (2017), who found a significant difference between pre- and post-intervention scores among physicians, nurses, technician, and auxiliary workers at Zagazig University hospitals [8].

4.1.1 Variation of knowledge according to different factors

The current study results revealed that both pre- and post-knowledge scores were significantly higher among nurses compared to housekeepers. Also, knowledge scores were significantly higher among workers attaining technical and university education than basic education.

Similarly, Soyam et al. (2017) in India reported that the overall knowledge of HCWs was high but the nursing staff was excellent. This could be explained by the fact that most of the study subjects received superior training on biomedical waste management (BMWM) frequently and approximately half of the HCWs had received training within 1 year. Also, in the same study, workers with a diploma in general nursing midwifery (GNM) had a higher level of knowledge on BMWM than other professionally qualified workers. Technical staff had significantly lower knowledge scores on BMWM than all nursing staff [6].

In addition, previous studies in India reported that the difference in the knowledge of nursing staff regarding the color coding system of bags for bio-medical waste was statistically significant [6, 9]. Nursing staff know much better in which bag the infected waste should be disposed of than other workers. This was attributed to the fact that nurses were more involved in applied work and tasks given by higher authorities [10].

The results of the present study are different from those revealed by another study from India, which found that the knowledge of the existence of biomedical waste management rules was better among doctors than nurses or paramedical staff, but that knowledge of the practical aspects of biomedical waste management was better among nurses and paramedical staff [11].

Hakim et al. (2014) assessed the KAP of health-care providers towards waste management at Ain Shams University Hospitals, Egypt and reported that knowledge about the presence of department plans and a hospital system for waste handling was significantly better among housekeeping staff than among nurses or physicians. On the other hand, the housekeeping staff in their study were less knowledgeable about specific details of management [5].

With regards to the association between the duration of employment and overall knowledge, the current study found higher levels of knowledge score among senior workers. Similarly, previous studies have reported that the years of experience in the hospital is significantly correlated with the level of knowledge [6, 12].

In addition, a study carried out in Iran, found that knowledge was highest in the 30 to 40 years’ age group and lowest in the group aged more than 50 years old [13]. Moreover, another recent study reported that the age and work experience of the study participants were significantly associated with knowledge regarding biomedical waste management (BMWM) [14].

However, another study found that younger workers (26–30 years) had higher knowledge of BMWM [6]. These conflicting findings may be attributed to the adequacy and frequency of training sessions conducted in the respective study settings [14]. In general, most of the literature agrees that knowledge regarding biomedical waste management was better in older and more experienced staff.

4.1.2 Variation of attitude according to education and job description

In the present study the post-attitude scores were significantly higher in workers with technical and higher education compared to basic education. Similarly, a previous study revealed that diploma holders had better attitude than educated workers with lower degrees [15]. Also, Soyam et al. (2017) in India found that senior secondary level educated respondents were more compliant with BMWM [6].

In agreement with the present study results, which found that nurses have a significantly higher knowledge score than housekeepers, a study in three hospitals at Menoufia Governorate, Egypt, where the majority of nurses (89.4%) in the study settings had high level of knowledge and high performance about hospital waste management [16].

4.1.3 Variation of practice according to different factors

The present study revealed that practice scores were significantly higher post-intervention compared to pre-intervention and the variation of both the pre- and post-practice scores were significantly noticed in nurses more than housekeepers.

Improvement of practices scores obtained in the current study are consistent with results of Pratinidhi et al. (2014) who reported that in pre-training observation there were 83.9% of biomedical waste handlers in the poor practice category which decreased to 2.1% post-training [17].

In addition, Hosny et al. (2018) showed that the 80.0% of the pre-training poor practice score changed to 0.8% post-training and that the 1.1% in the good practice category increased to 92.1% post-training [18].

Moreover, a study in India found that the practice scores of nurses were significantly higher than those of physicians (84.8% versus 67.3% had overall satisfactory practice). The authors explained this difference with the lack of training, as fewer physicians had received training on proper waste management during the course of their study [6].

Also, Gupta et al. (2015) revealed that the practice score was poor in 62% of sanitary workers and was average in 38% of them. After application of the training program, there was a significant decrease in the number of subjects who had poor practice scores (from 80 to 0.8%). These findings highlighted that the educational intervention was very effective and may be attributed to the clarity and direct applicability of the practical skills offered in such programs [19].

In the present study there was no significant association between previous waste management training and a change in KAP scores after intervention. These results came in agreement with previous research which confirmed that this does not reduce the importance of training courses and orientation programs on awareness about waste management, it does however raise an important question regarding the ability to improve practice in healthcare workers [5].

Another cross-sectional study in Egypt showed that, although attendance of training programs on waste management was the only statistically significant independent predictor of health-care staff’s knowledge, no such correlation was found with actual practices [20]. Another aspect that could affect the impact of training programs in the present study are temporary jobs, lower education levels for housekeepers and high turnover of nurses.

Researchers have suggested that most training courses and orientation programs emphasize theoretical aspects with numerous lectures but minimal hands-on training. Moreover, training programs should take into consideration the educational level of housekeepers, since a significant proportion is illiterate in developing countries [20, 21]. Finally, intervention studies play an important role in reflecting the effect of waste management programs on the KAP of workers. Most of them can improve the KAP of healthcare workers taking into account national guidelines and challenges.

4.2 Strengths and limitations of the study

This study is an intervention to test the effect of an educational program on the KAP of HCWs, explore possible factors that may affect their KAP and recommend the measures required for best practice in waste management. However, the study did not include physicians and was a single center study. The Cronbach’s alpha for the tool is moderate. Rapid turnover & lower educational levels of housekeepers are challenging for hospital administrations with regard to the application and evaluation of the immediate outcomes from training programs.