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Effects of noise on body functions:
- Medium frequency noise often causes hearing loss.
- High frequency noise (>1000Hzt) and high intensity (≥85dBA) first often causes hearing loss and then if exposure time is prolonged, it will lead to occupational deafness.
- With low frequency, noise on ships, although at low frequency < 500 Hzt, does not cause occupational deafness, but it affects the body continuously from day to day, causing nervous system tension, functional neurological disorders: headaches, dizziness, sleep disorders, fatigue. Neurological disorders can create prolonged anxiety, memory loss, high blood pressure, gastric ulcers - duodenum... That reduces the health of crew members, increases errors or inaccuracies in work, and can easily cause accidents [23], [26], [65], [105].
- In addition, if noise is combined with vibration, it will have a "synergistic" effect, increasing the harmful effects of each other many times [24], [70], [72], [80]. The two factors of noise and vibration on ships are the most harmful factors affecting the health of crew members. According to a study by Pham Hong Hai [23], which measured the hearing of 238 crew members, no cases of occupational deafness were found, but mainly the manifestation was hearing loss, especially those with high working age (over 6 years) and working in the engine room. If working on a ship for 5-10 years under the impact of noise exceeding the standard (over 85dBA), hearing damage will occur [115], [134].
Shaking and shaking on ships
Under the impact of the ship's engine operating at full capacity, combined with the effect of the waves causing the ship to rock, the worker falls into an unfavorable position, so the body must always perform reflexes to adjust the posture, so it requires the crew member to have stable vestibular and cerebellar functions.
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The effects of vibration on the function of organs in the body
depending on the amplitude, acceleration and frequency of the vibration:
- Very low frequency vibration (< 2Hzt ):
Often encountered in the movement of ships, vehicles, and airplanes combined with acceleration and low speed often leads to a specific disease that people often call motion sickness [24], [92], [93], [110].
- Low frequency vibration (2 - 20Hzt):
Often encountered in the operation of construction machinery, the main effects are spinal pain, sciatica, digestive disorders, neuromuscular disorders (reduced reflexes)... [111]
- High frequency vibration (20-1000 Hz):
This is a type of local vibration that directly impacts body parts that perform daily labor tasks such as hands, feet... resulting in specific occupational injuries that are called occupational vibration disease.
Vibration and shaking have a negative impact on the circulatory and nervous systems as well as the skeletal system. It has also been observed that vibration and shaking affect the biochemical components of the blood. Many authors believe that vibration and shaking increase the harmful effects of noise on body functions. This is whole-body, low-frequency vibration, which is the cause of vestibular disorders with the manifestation of seasickness [107], [124].
According to the research of Nguyen Truong Son [46], [48] Bui Thi Ha [16], [17] on the mechanism of causing disturbances in the body's functional activities, especially the cardiovascular system function due to noise and vibration, it is due to the effects of noise and vibration on the axis of Cerebral Cortex → Hypothalamus → Pituitary Gland → Adrenal Gland. The adrenal medulla is a sympathetic postganglionic
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giant has differentiated into an endocrine gland, each time receiving nerve impulses from the sympathetic center in the Hypothalamus will secrete catecholamine.
In this case, the impact of vibration on the cerebral cortex then follows the neuroendocrine axis Hypothalamus → Pituitary gland → Adrenal medulla, increasing the secretion of catecholamines leading to increased blood pressure...[58]
Marine lighting
Light is a physical element of the natural or artificial environment. Humans perceive information about natural and social phenomena 80% by visual means.
In labor, people set lighting standards for each type of labor according to different levels of precision requirements.
Table 1.2. Workplace lighting standards [4]
STT
Nature of work | Spot lighting | General lighting | |
1 | Very accurate | 1000-1500 | 50-100 |
2 | Exactly | 300-1000 | 40-80 |
3 | Fit | 100-300 | 30-80 |
4 | Rough | 30-100 | 20-80 |
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In the workplace, lighting is a factor that greatly affects labor productivity, labor quality and labor safety. Inadequate lighting also causes eye pain, eye fatigue, reduced vision, headaches and is often the cause of work accidents [116].
Electromagnetic waves and ultra-high frequency waves
The effects of these types of waves mainly affect the health of radio operators, control officers and those who operate the ship's radar system (navigation radar, collision avoidance radar, radio...). These types of radiation, in addition to generating heat and increasing body temperature, also have a direct impact on the health of the human body.
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contact with other parts of the body, especially sensitive to tissues with a lot of water such as the lens, testicles, intestines, liver, nerves. Dewaden, Gałuszko K. Institute of Marine and Tropical Medicine, Republic of Poland [81] observed that among telegraphers working on ships with an age of 5-15 years, there were higher rates of dysfunction of the nervous system, circulation and visual impairment than other groups of crew members. Studies by Filikowski J. also at the Institute of Marine and Tropical Medicine, Republic of Poland [88] found that people exposed to radiation often had a number of disorders such as: headache, insomnia, poor memory, decreased sexual activity, general fatigue, and weight loss.
1.2.3.3. Chemical factors
During the working process on the ship, the crew members also have to come into contact with many other toxic chemical agents [104]. According to Nguyen Van Hoan and Vu Tuyet Minh [25], the concentration of gasoline vapor is 4 times higher than the permitted standard. In addition, the fumigants used to preserve the goods transported on the ship also cause suffocation and discomfort for the crew members. Filikowski J. [87] commented that ship smoke and plastic products used in the shipbuilding industry also contribute to the feeling of discomfort for the crew members.
1.2.3.4. Biological factors
Crew members are at risk of contracting dangerous diseases if they come into contact with animals and insects on board such as rats, cockroaches, flies, and mosquitoes carrying pathogens...
There is also the risk of exposure to people carrying dangerous pathogens such as hepatitis B, C, HIV/AIDS... [36], [71]. These are high-risk factors for the health of the crew.
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1.2.3.5. Abrupt changes across different climate zones
Nowadays, ocean transport is greatly affected by the rapid development of shipbuilding technology, ships are increasingly modern, the speed of movement of ships is also increasingly fast, it can move through geographical areas, through oceans with very different climates and time zones in a very short time, this sudden change makes it difficult for the body to adapt immediately and as a result, crew members with poor health or poor adaptability will suffer from body dysfunction, susceptible to some diseases of the nose, throat, nerves... [49], [75], [82], [84], [117] and if this condition persists, it will have adverse effects on health and diseases such as insomnia, flu, rhinopharyngitis,
... leading to reduced working capacity of crew members [17], [18].
1.2.4. Social conditions, labor organization and nutritional hygiene on ocean-going ships
1.2.4.1. Micro-social conditions on board
During the journey at sea, sailors are isolated from their daily social life on land. All their activities and work are limited within the narrow space of the ship. On the other hand, the micro-social environment on board a ship is a special environment, with only one gender (homosexual society), creating a psychological burden for sailors. Therefore, it has caused sailors to lose psychological balance, easily developing functional neurological disorders, psychological disorders and mental behavioral disorders. Many authors believe that among the types of psychological-social burdens of the seafaring profession, sailors have to endure:
- Isolation from the mainland during the ship's voyage at sea;
- Long-term separation from family, society, friends, relatives;
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- Difficulty in using free time on board;
- The separation from their wives, partners and the opposite sex in general has caused the crew members to feel sexually stressed. This has led to the consequence that when they arrive at port, regardless of their health, they are willing to have sex with prostitutes, making it very easy to get infected with sexually transmitted diseases (STDs). Those who are afraid of disease may masturbate or have homosexual activities, leading to an increased rate of behavioral and mental disorders [53], [75], [79].
In addition, seafarers are also isolated from the social, political and cultural community on land and lack information, which is also a significant psychological and neurological burden [64], [83], [109], [123].
To maintain the continuous operation of the ship at sea, the crew is required to follow a shift system (each worker works 2 shifts a day, each shift is 4 hours), the idle time they spend partly sleeping, the rest is actually surplus time. When free, a worker on land often participates in activities such as serving the family, entertainment, social relations, but on a ship, the crew does not have the conditions to do these things. Although, nowadays, many modern ships are quite fully equipped with training, entertainment, and recreation facilities, the people living and working on the ship cannot change the space, place of residence, environment as well as the people living around them when the ship is on a journey at sea. All their time follows a rather monotonous and boring schedule: eating, sleeping, playing, and waiting for their turn to go on a shift, thus causing an unstable psychological state [6], a boring life and easily leading to negative, unhealthy activities such as gambling, smoking, alcohol addiction, and they often allow themselves to "let off steam" as soon as the ship docks. This often brings consequences from social evils to crew members [75], [96], [128].
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The issue of labor organization during sea voyages also has a significant impact on the health of workers. Labor organization during sea voyages is often very strict and rigorous, similar to that of the military. Their activities are often monotonous and boring, repetitive, and boring. The result is a state of psychological stress, which negatively affects the health of crew members [76], [85].
1.2.4.2. Nutritional conditions on board
Nutrition also has a significant impact on the health of seafarers [126]. Nutrition has long been a concern not only for seafarers themselves but also for many marine medical researchers. Since ancient times, when people used primitive means of navigation to cross the sea, the issue of providing and preserving food, food and water for long sea voyages has always been a top concern for seafarers.
Nowadays, the provision of food, food, and drinking water for seafarers has made great progress. However, preserving the quality of food is still difficult, especially the preservation of fresh foods such as vegetables, fruits, meat, etc. Preserving vegetables is not only a difficult problem for Vietnamese ships but also for foreign ships with modern equipment, because vegetables are preserved in cold storage but after 5-7 days, the vegetables still deteriorate, gradually lose nutrients, especially vitamins, and when processed, they do not bring the same delicious taste as when the food is fresh [139].
According to research by Bui Thi Ha and colleagues [17], meals on ships are often monotonous and nutritionally unbalanced, especially lacking in vitamins. The lack of vegetables in meals also causes a lack of fiber, a major substance that increases intestinal motility and prevents constipation, thus easily causing diseases.
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The reason is lack of fiber, lack of vitamins. Research by Nguyen Thi Ngan and colleagues shows that the rate of VOSCO crew members suffering from digestive diseases, especially constipation and hemorrhoids is very high [39]. Research by Nguyen Truong Son and Tran Thi Quynh Chi on the characteristics of the working environment and its impact on the health of seafarers also gave similar results [52].
An unbalanced menu on board will cause a series of metabolic disorders in carbohydrates, lipids, and proteins, increasing the risk of cardiovascular and blood pressure diseases. People with seasickness are at even greater risk of malnutrition due to frequent vomiting [136].
The role of nutrition for seafarers is very important, so we need to have research projects on nutrition and nutritional regimes for Vietnamese seafarers.
1.2.4.3. Environmental sanitation on board
On ships operating at sea, the conditions for handling and maintaining ship hygiene are much more difficult than when the ship is docked or on land. This is even more evident on small ships where the accommodation is also the place for living and working, all confined within the framework of the ship's four iron walls, environmental hygiene conditions are not guaranteed, many ships do not strictly implement the 3-kill regime periodically, so there are often insects and disease-carrying animals on board. According to the research results of Nguyen Van Hoan and Vu Tuyet Minh [26], Nguyen Ngoc Khang [29], Nguyen Lung [33], [36], Nguyen Truong Son [51], [52], maintaining hygiene on ships is difficult because the space inside the ship is too narrow, the living and production areas are adjacent to each other, the hygiene awareness of the crew is not high, the 3 extermination work (exterminating flies, mosquitoes, cockroaches, rats) is almost not carried out on ships or if it is carried out, it is only perfunctory. These conditions make the rate of infectious diseases among crew members quite high.