Our study aimed to clarify the reasons behind differences in OHS among these countries. In order to achieve this goal we compared the OP/workers ratio and the scope of OHS provision in 20 countries with their corresponding macro-economic indicators of GDP per capita, health expenditure per capita, and GI. We found a significantly negative correlation between health expenditure percentage of GDP and OP/workers ratio. Additonally, significant positive correlation was found between the GI and the OP/workers ratio. Negative correlation means the higher health expenditure percentage less workers are treated with one OP, meaning higher rate of OP/workers. Positive correlation means that higher GI (inequality) correlates with more workers per one OP, meaning lower rate of OP/workers.

There are some drawbacks to our study. We got enough data for only 20 countries. Usually reports come from developed countries so it might give bias status considering the status of OHS. There are difference among countries like the industry mix of the country’s economy or OHS regulatory/legal system which could influence the OP/workers rate. Other professions within OHS like nurses, ergonomists, hygienists, employee support, health and safety managers etc. were not considered. The number of OP is relevant to the year of publication.

To the best of our knowledge, no other publication used these parameters to evaluate OHS between countries. Radon et al. [21] compared different parameters of OHS among eighteen countries including the fatality rate of work-related accidents, accident insurance systems, and workers' compensation in case of an occupational accident or the coverage of occupational disease by the workers' compensation insurance. We think that these parameters are easy to trace but do not represent the full scope of OHS, but rather, the government’s actions concerning workers’ safety, enforcement of safety regulations, etc. We believe the workers' compensation system represents the policy of national insurance and private companies in each country and not necessarily the scope of OHS.

Westerholm et al. [3] compared eleven OHS. They found that the countries which strictly enforce by law the provision of OHS can, for obvious reasons, demonstrate high rates of workforce coverage, approaching 100%. We agree this is a good parameter (representing the availability of OHS but not necessarily the quality). However, in most countries, it is difficult to conduct reliable assessments due to statistical uncertainties—in the UK, Japan, Austria, Sweden, and the Czech Republic estimates were particularly imprecise [3]. In most countries in this review, the funding of OHS was supported by client companies and employers. Radon et al. [21] showed that in the majority of the 18 countries represented in their research, the premiums for OHS were paid only by the employer and hinged on the risk and size of the enterprise. After reviewing the literature, we conclude that, in almost all countries, OHS are paid by the employer, thus making the parameter of OHS funding immaterial in trying to com-pare services between different countries.

The National Institute for Occupational Safety and Health (NIOSH) established some strategic goals that best represent the health and safety issues facing the US workforce [25]. Among these goals are reducing the rates of occupational cancer, cardiovascular disease, occupational hearing loss, occupational musculoskeletal disorders, etc. There are several difficulties in converting these strategic goals to parameters that could evaluate OHS. An occupational disease registry could help monitor and evaluate trends in occupational disease as outlined above. However, in most countries, these registries are voluntary and do not represent true rates. Another difficulty would be the latency period for an occupational disease which could take 10–20 years to manifest. Other goals depend on the employer's attitude towards occupational safety and health. In light of the above, we believe these parameters are difficult to trace and analyze in most countries, due to their subjectivity and wide variability and would not be used as a good monitor for OHS.

We also believe that all parameters presented thus far are prone to be influence by many factors such as employer attitude, safety regulations, degree of enforcement, insurance legislation, etc. When we compared different services of OHS we found that FFW differentiate better since pre-employment examination service and periodic health examination service is given in all countries, and only FFW services is given in several countries, definitely not in many, as other service. However, whether FFW evaluation is given does not explain well the gap among different OHS.

Consequently, we propose the OP/workers ratio as an easily measured and simplified method of comparing OHS among different countries. This notion is not entirely novel. In 2002, Rantanen et al. [26] published a review on OHS in Europe. They found that the ratio of OP/workers and occupational health nurses/workers in Europe varies between 1 per 500 and 1 per 5,000. Nicholson [27] considered the challenges facing occupational medicine in the UK and how to improve access to OHS in 2004, and concluded that there are no readily obtainable comparable data particularly concerning full-time/part-time status, practicing/retired members, and level of qualification/training thus making this benchmarking difficult. We postulate that currently available data in the medical literature and other online resources make it easier to benchmark.

The primary debate is how much of the data found in our study truly represent the status of OHS. We were not able to evaluate the quality of OHS since quality is difficult to measure and data is missing from most country registries. We found that the scope of basic OHS is different between countries, but that this difference is not explained by the disparity in OP/workers ratio. Nonetheless, we propose to focus on the status of three countries with high GDP/capita and low workers/OP ratio (South Korea, Israel, and the USA) and examine whether a low ratio truly represents disparities in OHS in these countries.

The rate of OP/workers in South Korea was 1:53,350. South Korea OHS are provided mainly by private OHS institutions outside the workplace. Very few workplaces have their own services. Occupational medical examinations for workers exposed to potential work hazards must be provided within paid working hours at the employers expense [10]. However, most employers in small businesses tend to ignore or neglect the OHS because they have limited resources than large businesses. In 2011, the South Korean government launched regional public Workers Health Centers to provide small businesses with basic OHS. These centers are staffed by OP and are free of charge. In 2019 approximately 20 workers health centers are operating. According to the South Korean labor force there is an urgent need to extend this program [11].

The rate of OP/workers in Israel was 1:44,078. In Israel, in contrast to other developed countries, OHS are socialized and available to every employee in the country under the National Health Insurance [17]. The OHS are anchored by legislation; some services such as health surveillance of workers exposed to specific hazards are required of employers to be performed by law, while other services are essentially a given right to every worker. Research in the field of occupational medicine in Israel is currently scant [17]. Contrary to the norm in most Western countries, there is currently no National Institute of Occupational Health in Israel that focuses on environmental and occupational health in the workplace. Another concern is outdated occupational standards and regulations that were last updated in the 1990s. Consequently, many sectors like the agriculture and construction industries, and small workplaces with less than 50 workers, are overlooked.

Baker et al. [19] reported, based on demographic data provided by the American College of Occupational and Environmental Medicine (ACOEM), that in 2007, 4,725 physicians were registered ACOEM members leading to a respective OP/workers ratio of 1:34,766 (Table 1). We did not find the coverage rate of the US working population, but we assume it is probably the same than the UK (12%). Also, the OHS in US includes only pre-employment and periodic health examination. The low availability may manifest in high occupational injury and illness rates. Injuries at work comprise a substantial part of the country's injury burden, accounting for nearly half of all injuries in some age groups [28]. Souza et al. [29] evaluated different parameters to estimate disparities in occupational health in the US. They suggested parameters like work fatalities, work accidents, work-related disease, health claims data, etc. We have explained why many traditional parameters such as these are less accurate and multi-factorial, and hence better not be used to estimate occupational health.

Surveillance of a health disparity necessarily involves defining the disparity and deciding how progress towards reducing it will be measured. We think the data collected in our research show that the OP/workers ratio is a parameter both easy to define and can be obtain which best represents the availibility of OHS in either country, as it correlates with GDP per capita, Health expenditures and GI. The implications of the data collected in this study are that we are still far from fulfillment of the concept of “Occupational Health for All”, and that there is much to be done in this field. Last but not least is the question of what should be the ultimate ratio. In developed countries (GDP per capita > US$30,000) it seems that an OP/workers of 1:5000 is a reasonable and acceptable ratio to support proper and accessible OHS to the working population.