الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Organic solvents are volatile organic compounds that evaporate at room temperature and are used as solvents. They include aromatic compounds such as benzene, toluene, xylene, alcohol such as methanol, esters and ketones such as acetone, nitro-hydrocarbons and halogens. Benzene, an organic solvent, is a mixture of hydrocarbons and additives . However, the components of gasoline depend on the source of crude oil and the refining process and the laws of each state . Benzene, toluene, ethylbenzene and xylene (BTEX) Are the main toxic components of gasoline, including benzene specified to be the most dangerous .
Most color vision tests (eg Ishihara panels) were originally designed to detect congenital color vision defect, ie changes in the red-green axis, but low sensitivity in the study of acquired color vision defect resulting from chemical exposure where most changes are found in the yellow-blue axis .
With respect to the acquired tests, the lanthony D-15 desaturated test is considered Is the most appropriate and sensitive in field studies, since it has the potential to quantify results, which greatly improves the comparison of results between exposed and reference workers, and allows the study of dose-effect relationships .
More recently, some studies have shown the rise of some oxidants in workers exposed to organic solvents. The toxic effects of organic solvents are reported to be associated with reactive oxygen species (ROS). Free radicals are high-reaction types that interfere with cellular damage and are believed to stimulate lipid peroxidation, which in turn destroys biological membranes.
One of the important areas that workers may be exposed to organic solvents is the gas station . Benzene contains a lot of organic solvents that can cause harmful health effects, especially benzene, toluene and xylene .
Subjects and methods
The study extended for about 40 months The study was conducted in three stages:
I . Preparatory stage II . Operational phase III . Analytical stage
I . Preparatory stage Included: write protocol and approval, develop a questionnaire and seek permissions.
Preparation of the study
The study was conducted at some of the fuel stations in Alexandria, the occupational health and air pollution laboratories, the Higher Institute of Public Health, the University of Alexandria, and the laboratories of the Department of Technology Management, the Egypt-Japan University of Science and Technology. An ophthalmic examination was conducted at the site and at an oil hospital.
Target population
The study was conducted on 200 workers divided into two groups of 100 workers registered in the study:
• The first group contains 100 workers (exposed group) : This includes workers who are chronically exposed to gasoline at some petrol stations in Alexandria
• The second group contains 100 workers (non-exposed group). ” A group of workers who are not exposed to benzene and were matched to age, gender and socioeconomic status was studied as a control group The inclusion criteria: 1. Workers exposed to gasoline at a petrol station, working 8 hours / day, 5 days / week for at least one year, as in previous studies <2. Workers aged 20-55 years
Exclusion criteria:
1. Workers over the age of 55 years as changes in lens color known as nuclear sclerosis may affect the results of color vision tests.
2. Workers with congenital malformations such as congenital chromosomal blindness, congenital glaucoma, congenital white water, and congenital retinal diseases.
3. Workers with systemic diseases such as diabetes and high blood pressure.
4. Staff suffering from diseases in the front of the eye such as corneal opacity, corneal atrophy or decay, cataracts and glaucoma. 5. Workers suffering from diseases of the back of the eye as diseases of the retina and retina.
Study procedures The study was conducted in two stages:the first phase was carried out among exposed and non-exposed populations
Phase 2: The exposed group was divided into two sub-groups. • Subgroup A includes positive cases. • subgroup B include negative cases
Electrophysiological tests were performed for a representative sample of positive and negative group. Sample size 100 workers for each group and the representative 30 workers for each selection method and sampling technique We chose 4 stations in 4 different locations in Alexandria. Some in crouded areas and others on the highway; to achieve the required number of vulnerable group to avoid the impact of absenteeism and lack of cooperation. II . Operational phase and data collection 1. Interview and questionnaire A detailed questionnaire will be applied to both exposed and non-exposed workers to gather the following basic information: • Personal and demographic data: name, age, sex, date of birth and marriage • Professional data, Smoking habits, Medical History, and ophthalmological examination:For each eye, the following tests were performed: General tests for ophthalmology: . manifest refraction and best corrected visual acuity using Snellen chart, light reflex by direct and indirect method, measurement of eye pressure IOP and examination of anterior and posterior chambers o the eyes
Color vision test
Pseudoisochromatic plates (Ishihara) to exclude congenital workers in congenital color vision. Lanthony d15 desaturated test was used for detection of acquired dyschromatopsia with interpretation of the results using moments of inertia, t,t-MA, MA, HA and Mha were used as biomarkers for BTEX in gasoline and MDA and TAC were used as parameters of oxidative stress.Results
62% of each eye of exposed workers and 5% of non-exposed workers had acquired dyschromatopsia. Of the total exposed 44% had complex type of acquired dyschromatopsia. Quantitatively, there was significant difference between both groups regarding confusion index (p ≤ 0.015). Also, there were significant differences between both groups regarding levels of biomarkers of exposure to BTEX and antioxidant levels. It was also found there is dose response relationship with strong positive linear correlation between biomarkers of exposure and confusion index, as well as with MAD as biomarker of oxidative stress.