The agricultural work is associated with a series of adverse health effects. The causation of the work related problems is being discussed in many research papers. The extensive literature review revealed a series of factors that have been found to be directly or indirectly related with farmers' health. These factors fall into five major categories, namely the exposure to hazardous agents, the type of agricultural work, the level of use of Personal Protective Equipment (PPE), specific demographic characteristics and finally cognitive factors. The understanding of the above parameters is of great importance for Primary Healthcare and, in specific for the support of one of its functions, which is Occupational Health and Safety. The aforementioned parameters are interrelated through a specific schema, which in fact describes the occupational health and safety considerations. The current study describes the modeling of the above internal process of the agricultural work. This is achieved through an object oriented modeling procedure that may be used from one part for the overall understanding of farmers' health dynamic by primary healthcare professionals and from the other part as a tool to support the process of the development of Primary Healthcare and Occupational Health and Safety Information Systems in rural areas.
The agricultural work is associated with a series of adverse health effects, which are mainly caused by exposure to pesticides, allergenic agents, bad posture and weight lifting. Asthma and rhinitis are the most common respiratory symptoms among farmers . Dispnea, wheezing and cough are equally common symptoms. In addition an increased number of cases of allergenic rhinitis and respiratory problems among grape farmers are reported . Malignant diseases are also related with farming. The main cause is the exposure to pesticides. A perspective study that was carried out in 2005 among carbofuran applicators indicated a very high relative risk (RR=3.05) for the development of lung cancer . It has also been found that the use of the pesticide diazinon is related with the development of pancreatic cancer . Accidents also consist of an important hazard for the safety of farmers. In Great Britain the number of occupational accidents in the agricultural sector is the highest among other industries . Most accidents are related with the use of vehicles  and machinery, falls and electrocution.
In many countryside regions, the majority of individuals who visit Primary Health Care facilities are occupied as farmers and stock breeders. Due to their occupation, they are exposed to various hazardous agents, thus the need for an effectively organized health record could efficiently be used for the improvement of the surveillance of farmers' health. The role of Primary Care as the main supportive structure of farmers' occupational health, should be understood in order to contribute to the effective prevention of risk factors causing occupational diseases, the efficient, focused education of farming population on the proper use of PPE and finally the better understanding of the primary causes of farmers' symptoms and diseases.
Health data collected in Primary Health care centres in rural areas is not easily utilizable for the efficient surveillance of the patients' health. The development of Electronic Health Records specifically designed for Primary Healthcare Organizations is crucial and focuses on a series of challenges . Evidence based practices in the clinical process, supported by Health Informatics in Primary Healthcare is also considered of uttermost importance . The use of Informatics in Primary Healthcare settings of developing countries mainly focus on the development and implementation of information systems as well as on decision support and information exchange systems . A carefully designed Health Information System which includes fields related with occupational health of farmers could be used as a tool for the efficient surveillance of farmers' health in Primary Care. The use of information systems for this purpose is not an unknown practice as many studies describe such practises .
Factors associated with farmers' occupational heath
According to the literature, specific production types are associated with the prevalence of certain diseases among farmers. The understanding of the special characteristics of each agricultural work may contribute to the identification of type-of-production specific occupational diseases. Grain farming is associated with the development of respiratory problems, due to the inhalation of grain. Asthma and rhinitis are quite common symptoms among grain farmers , . This production type has been proved to be related with the development of various cancers and leukemia. , , . Cereal farming has also been associated with malignant diseases  and non-Hodgkin lymphoma . Regarding fruit cultivation, it has been found that it is associated with skin allergies , , whereas, greenhouse working is associated with musculoskeletal problems, among others .
Use of PPE is considered to be of uttermost importance in relation to the farmers' health and safety. According to numerous reports and guidelines, proper use of PPE may decrease the risk of developing occupational diseases or involving in occupational accidents. , ,  Inevitably the level of exposure to the various risks related with the agricultural work, is an obvious parameter which should be taken into account in order to accurately describe the profile of occupational health and safety for an individual farmer , . Many resources state that extended work in the fields is related to increased chance of an accident , .
Added to the above, individual and demographic characteristics of farmers seem to be related with specific practices in agricultural work, thus leading to different exposures. For example, women are reported to use gloves less frequently  and young, educated male farmers use better protection when working with pesticides . In addition it seems that farmers with bigger lands also use better protection of PPE .
Cognitive parameters, namely the level of knowledge on proper good practices, as well as the perceptions regarding health and safety in agricultural work also seem to be of great importance and should be taken into account in order to thoroughly understand the direct and indirect health risks among farming population. In specific, it has been found that farmers' level of knowledge about risks in agricultural work may be correlated with the level of use of Personal Protective Equipment . Another study that was conducted by Mandel et al  found that there are differentiations of the farmers' beliefs regarding the hazardous effects of pesticides. In addition the authors found that the proper use of PPE is related with the perception that using protective clothes is an effective protective measure. Finally, according to Schenker et al.  better use of PPE is related with the perception that the agricultural work is safer compared with other professions.
The understanding of the importance of the above actual, cognitive and behavioural factors, which have been shown to be directly or indirectly associated with farmers' health and safety, is of uttermost importance. This is particularly true in the field of Primary Care of rural areas, due to the fact that each of these categories is part of the farmers' occupational Health and Safety. It is of great importance to be conceptualised that a major role of Primary Care is Occupational Health and Safety in the Community. Based on this, Primary Healthcare Organizations in rural areas should benefit from the understanding of these factors, and utilise this information for the efficient surveillance of farmers' health and the understanding of the underlying causes of developing a disease. The systemic approach of the above health and safety factors can be illustrated through an organized schema, which describes the inter-relationship between them.
This process can be considered as part of the risk assessment process. The term risk assessment describes the careful examination of what could cause harm to people in the workplace, in order to avoid accidents and ill health. According to HSE (Health and Safety Executive of the UK), risk assessment is a five stage process which involves looking for the hazards, deciding who might be harmed and how, evaluating the risks and deciding upon the adequacy of the measures, recording the findings and finally reviewing the assessment. It is therefore considered to be a systematic procedure to identify potential health hazards, evaluate the extend of exposure and establish the effectiveness of the existing measures 
Modelling the health and safety process of the agricultural work
A prototype for a universal object-oriented model describing the general process of Occupational Health and Safety in Agriculture is based on the objects that directly or indirectly interfere with farming health (see above). Extensive bibliographic research for the understanding of the farming work led to the identification of the major parameters in the farming work that may lead to occupational diseases or accidents. Within the use of a UML class model, major object classes have been defined and also their subclasses, associations and attributes. The top-down design approach allows use, reuse, and cloning of the standard components.
Object-Oriented Modeling is a modeling paradigm which assists the system designer to address the complexity of a problem domain by considering the problem not as a set of functions that can be performed but primarily as a set of related, interacting objects . The modeling task then is specifying those Objects, their respective set of Properties and Methods, shared by all Objects members of the Class. The description of these Objects is a Schema. The Model description or Schema may grow in complexity to require a Notation. Many notations have been proposed, based on different paradigms, diverged, and converged in a more popular one known as UML. Object-oriented paradigm has become the standard approach throughout the whole software development process as well as for the analysis and design phases within a software development process, where object-oriented modeling approaches are becoming more and more the standard ones. 
The proposed object-oriented model
According to the systematic literature review, it has been found that the factors which are directly or indirectly related with the occupational health and safety can be included in the following categories, which consist of distinct objects in the proposed object-oriented model. The objects that are identified, which have been discussed earlier in this paper, are described in Table 1.
Prevalence of work related diseases and symptoms among farmers
Frequency of use of PPE in the farming population
Farmers' knowledge and perceptions regarding occupational health and safety
Demographic characteristics of farmers
Duration of the exposure to the agricultural work
Type of production
Table 1: objects describing the occupational health and safety of the agricultural work
It should be noted that the proposed model does not include those factors that affect farmers' health as a whole (ie. dietary habits, quality of primary healthcare support etc) but only those parameters that are found to have an effect on the working environment, namely those that interfere with specific practices and characteristics that underpin the agricultural work.
Each object is given a specific code (OBJ_01, OBJ_02 etc) which will be used as an abbreviation in this section. The definition of the objects is followed by the formulation of the inter-relationships between them. According to the systematic review results, it has been found that OBJ_02 (Use of PPE) is related with famers' health (OBJ_01). In addition, OBJ_03 (knowledge-perceptions) is directly related with OBJ_02 (Use of PPE), which in turn is related with OBJ_01 (farmers' health). OBJ_04 (demographics) are indirectly related to OBJ_01 (farmers' health) through OBJ_02 (Use of PPE). Furthermore, OBJ_05 (duration of exposure) and OBJ_06 (type of production) are directly related with OBJ_01 (farmers' health).
There are certain specific attributes within each object, which seem to have greater impact on these relationships. For example, in relation with OBJ_03 (knowledge-perceptions), it seems that the level of knowledge on agricultural risk factors and the perceptions on the need of use of PPE have a significant positive effect on OBJ_02 and, consequently on OBJ_01. As a matter of fact the same effect is indicated in the case of OBJ_04, in which the attributes age, gender and educational level are the major identifiers of OBJ_04. Figure 1 presents a conceptualized object oriented-schema based on the above mentioned relationships.
Figure 1: object-oriented model describing the health and safety process in the agricultural work
The agricultural work shares some unique characteristics in relation to the health and safety of farming population. Due to the fact that farmers are self-occupied there are no distinct structures to support occupational health and safety, as it happens to other industrial and office work areas. Primary Healthcare should not only support the efficient follow-up of farmers' health in rural areas but should also identify the risk factors that related to the agricultural work, based on specific structures of occupational health and safety which are staffed with experienced occupational doctors and other health personnel. The proposed object oriented modeling procedure can therefore be utilized for the overall understanding of farmers' health dynamic by primary healthcare professionals. In specific, the perception of these dynamics are expected to support the prevention of work related adverse health effects and the efficient planning of focused interventions in the farming population, which take into account the specific job-related factors that may affect farmers' health, according to the proposed model described in this paper. In addition, this model may be used as a supportive tool in the process of development of Primary Healthcare and Occupational Health and Safety Information Systems in rural areas, as a guidance of the fields that should be taken into account and therefore included in the Information System. Such a system should be able to support more efficiently the surveillance of farmers' health and the epidemiologic research on this subject area.
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