Workplace related accidents are major cause of chronic illness and deaths in Singapore. According to the Center for Disease Control and Prevention (CDC), a total of 5702 work related injuries have been reported and the annual rate of death is around 4 deaths per 100000 workers (as calculated in 2005). The major workplace incidents result in morbidity, mortality and even rise in the socio economic cost of Singapore1. All the multinational corporations are introducing newer hazardous technologies that can have negative impact on the occupational health of the workers and the employees. Much research and experiments have already been conducted that provide significant evidence that this feature of global commerce poses a serious threat to the health, safety and even the natural resources. This also endangers the workers who are involved in the organization. The nations that are less developed are at higher risk of exploitation of the human resources because they lack the expertise, safeguards, and the public pressures that can help in the prevention of the harms that are caused to the workers (in developed nations). There are many approaches and interventions that are taken by the industrial as well as the international organizations to address the workplace hazards, with the help of soft law, or hard law, codes of conduct and the self regulation that is voluntarily done2. One of the occupations is leather tanning that is basically chemical preservation of raw hide and it involves the process in which various chemicals bind to the proteins. The workers are at the potential risk of exposure to many hazardous chemicals, most importantly chromium salts and therefore, are under threat of chromium toxicity. Presence of chromium and its compounds in the working environment leads to changes in the cytogenetics of individuals who are exposed to this chemical and may eventually cause abnormality in the ventilator functions i.e obstructive airways. A research study was carried out on the heparinized venous blood leukocytes. The results revealed that forced expiratory volume and the forced vital capacity for one second, were reduced significantly in the workers that have been exposed. Also the chromosomal aberrations were higher in the exposed workers. The sister chromatid exchange was also found to be higher in exposed workers3.Chromium and its compounds have proved to be very harmful for the health of the occupational workers. Chromium is an irritant the can cause perforation in the nasal septum, dermatitis, respiratory problems, hepatic and impairments of renal and gastrointestinal problems as well. Direct contact with chromium can stimulate its binding with the proteins of the skin and produce complex antigens that can cause hypersensitivity and even in some cases, dermatitis. Chromium and its compounds can enter the body in hexavalent form and can cross the cell wall and then convert into a more disastrous form that can initiate a series of chronic health disorders and conditions that may prove fatal for the survival of the workers3.
Relationship between chromium and its compounds and the potential harms
Chromium is monetarily essential in metallurgy, electroplating, and in different synthetic applications for example, colors, biocides and solid oxidizing operators. Unfavorable wellbeing impacts have long been known and incorporate skin ulceration, punctured nasal septum, nasal dying, and conjunctivitis. Reports of bronchogenic carcinoma showed up preceding World War II in Germany and were thusly affirmed in numerous studies.1 The International Agency for Research on Cancer (IARC) pronounced in 1980 that chromium and sure of its mixes are cancer-causing and, in 1987, presumed that hexavalent chromium is a human cancer-causing agent yet that trivalent chromium was not yet classifiable. Late studies overhauling chromium laborer companions in Ohio2,3 and Maryland1 exhibited an overabundance lung disease hazard from introduction to hexavalent chromium. The use of chemicals has become extensive in the industrial regions. Most of the important products are derived from harmful chemicals. Some of these products are fertilizers, fibre glass, pesticides, paints and even plastics. However, the lack of caution in the use of these chemicals has resulted in fatal occupational health outcomes. Some of the chemicals are so dangerous that they need to be properly stored in containers that are covered properly, for exposure into the air would lead to chemical conversion of the compounds and they might convert in more stable and more toxic compounds. Chemicals may be toxic, inflammable, reactive, radioactive or explosive. It is important to assess the hazardous potential of any chemical before putting it into use. For analyzing this it is important to identify the properties like inflammable nature, toxicity, radioactivity and reactivity of the chemical compound4. Chromium and its compounds fall in the category of incompatible chemicals, the chemicals that have the capacity to react with each other instantly and violently and their reaction leads to liberation of large amounts of heat or may, in some cases, produce flammable or toxic products. Chromium trioxide and chromic acid are the chemicals that have acetic acid, camphor, turpentine, glycerol, naphthalene and other flammable liquids as their incompatible chemical counterparts4. Chromium and its compounds also fall in the category of sensitizers i. e they are capable of causing or stimulating or inducing an allergic reaction. The intensity and the effects of the chemical however depend upon the susceptibility of the receiver or the individual who is exposed to the compounds of Chromium4.
The most promininet profession where the workers are at the maximum risk of counterfacing chromium toxicity, is chromium plating or manufacture of the dyes and the pigments. Even in the processes of electroplating and during the production and welding of stainless steel parts, chromium hexavalent) is utilized. Exposure to chromium is generally linked to fatal disorders of the lungs, and adverse effects to the nasal cavities and the paranasal sinuses5. Hromium is found to occur in mainly four different oxidation states: 0 (carbonyls, alloys and metal of chromium), II (the chromous compounds), III ( ores of chromite and compounds of chromic) and VI ( chromic acid, dichromates, chromates and chromium trioxides). The toxicity of the compounds of chromium depends upon the valence states of these compounds. And the valence states depend upon the administration of the solubility of these compounds. The toxicity exhibited by chromium is maily due to its hexavalent state and the potential to get reduced into trivalent state. The available literature deals with the pathomorphological changes in the organs of the animals when exposed to chromium toxicity. The effects of chromium are carcinogenic, mutagenic, teratogenic and embryotoxic effects. The experimental studies conducted on guinea pigs suggests that when high doses of chromium was administered to them, it resulted in renal injury and production of casts and albumin in the urine. There was also significant evidence that supported renala tubular damage in these animals and this was supported by the evidence of alterations in the activity and the functioning of different enzymes, glucosuria and proteinuria. Also, there was evidence of hypertrophy and hyperplasia6. In one of thestudy conducted on the effect of hazardous chromium on the Tannin industry workers, it was found that the tannin worker have the potential to be exposed to variety of toxic chemicals like chromium salts, organic solvents like formaldehyde, benze and benzidine based azo dyes. Those workers were mainly exposed to chromium salts like potassium dichromate ( used specifically in the section of the leather tanning. Chromium, being an irritant, can affect the nasal septum leading to problems in the respiration, causing dermatitis, or gastrointestinal infection and other chronic conditions. In its hexavalent form, chromium enters the cells and is immediately reduced to its trivalent form. Although chromium (III) is considered as a dietary mineral in low doses, Cr VI is carcinogenic. The hexavalent of chromium is corrosive in nature and carcinogenic and cytotoxic. Workers who are exposed to chromium are more prone to develop lung and nasal cancer. The free radicals can lead to oxidative change in the protein and may also cause mutations in the DNA or even damage the chromosomes7,8. Most of the publications have reported obstructive effects of chromium. There is some evidence about the after effects of soluble chromium also. It leads to initiation of symptoms like chest pain, cough, dyspnea and even development of asthma9.
According to a Risk assessment report that was published in 2005, five different chromium compounds and their effects on the health outcomes of humans was evaluated: sodium chromate, chromium trioxide, potassium dichromate, ammonium dichromate and sodium dichromate. The report was published in UK and the RAR identified the concerns and the fears of the workers who worked in the industries and the organizations that had high rates of chromium exposure. The Human health RRS was concluded and finished in 2007 and the commission had recommended the setting and establishment of EU wide occupational exposure limits. The report predicted the fatal outcomes in the health and the human concerns were mainly about the respiratory tract irritation, irritation of the skin and eyes, skin sensitization, occupational asthma, mutagenicity and carcinogenicity, reproductive toxicity (developmental and fertility toxicity) and acute toxicity which was majorly due to the short term peak inhalation of the chromium in the air14.
Receptive oxygen species (ROS) are an unenviable piece of vigorous life. Their unfaltering state focus is a harmony in the middle of generation and end giving certain enduring state ROS level. The element harmony can be irritated prompting improved ROS level and harm to cell constituents which is called "oxidative anxiety"10. This survey depicts the general methodologies in charge of ROS era in sea-going creatures and discriminatingly investigations utilized markers for ID of oxidative anxiety. Changes in temperature, oxygen levels and saltiness can result in the anxiety in common and simulated conditions by means of actuation of disbalance between ROS generation and disposal. Human borne contaminations can likewise upgrade ROS level in hydrobionts. The part of move metal particles, for example, copper, chromium, mercury and arsenic, and pesticides, specifically bug sprays, herbicides, and fungicides alongside oil items in incitement of oxidative anxiety is highlighted. A years ago the exploration in science of free radicals was refocused from just graphic attempts to atomic components with specific enthusiasm to ones improving resilience 11.
Oel and threshold limit for exposure to chromium
Research has found that the workers might be exposed to chromium VI, which can be present in the air due to its manufacture from other forms of chromium like the production of chromates from the chromium ore. According to the National Institute for Occupational Safety and Health (NIOSH), chromium VI compounds are potential carcinogens, which are associated with nasal, lung or sinus cancer. The criteria document released by NIOSH has reviewed the critical health effect studies of hexavalent chromium (CrVI) compounds. NIOSH has conducted a quantitative risk assessment of the effect of chromium and the most acceptable threshold levels of its exposure. According to Park et al. (2004), NIOSH recommends the threshold limit for the usage of chromium VI , not beyond 0.2 µg Cr (VI)/m3 for an 8 hour TWA exposure, during a 40 hour work week 12. The Recommended Exposure Limit is supposed to reduce the increased risk to lung cancer that is associated with occupational exposure to Chromium (VI) and its compounds. It is also expected to reduce the exposures that are air borne, in the workplaces and thereby ensure a significant reduction in the malignant respiratory effects including the perforated, irritated and ulcerated nasal septa. But since there are still certain levels of residual risks for lung cancer, NIOSH has recommended that continuous effort be made to reduce the exposures to CR (VI) and its compounds below the Recommended exposure limit (REL). The inclusion of Cr (VI) compounds in the category of potential carcinogens has been supported by scientific evidence. These compounds have shown to possess carcinogenic potential in invitro animals or humans 13.
The Immediate dangerous to life or health (IDLH) is a measure of how much threat the exposure has. It is a condition that possesses a threat of exposure to the air borne contaminants when the exposure has the capacity to lead to death or delayed long term complications in the health of the worker who has been exposed 13. The motivation behind building an IDLH worth is (1) to guarantee that the laborer can escape from a given defiled environment in the occasion of disappointment of the respiratory insurance gear and (2) is viewed as a greatest level above which just a very solid breathing device giving most extreme specialist security is allowed The IDLH for chromic acid and the chromates is around 15 µg Cr (VI)/m3 13.
In this manner, the tannery laborers are under high hazard and in a stage in which expulsion from further introduction to Cr is compulsory before cancer-causing nature get to be settled. The laborers ought to be made mindful of the wellbeing risks because of Cr15. Procurement of staff defensive supplies, consistent word related biomonitoring of air levels of Cr and gasses, at the working environment and the close-by surroundings that can be utilized as an apparatus to lessen the introduction danger to Cr and different contaminations in the tannery laborers, especially those with SCE. On the other hand, further studies are additionally required to elucidatethe unsafe impacts of trivalent Cr in a more extensive populace of tanning laborers3.
Reading between the lines and considering the available evidence on the use and rate of exposure to chromium and its compounds, in various industries that employs millions of workers, it is clear that chromium is palatable to a certain limit only and beyond that the dose of chromium or its exposure becomes hazardous leading to chronic nasal problems and cancers of lung and skin18. The mutagenic, carcinogenic and cytotoxic nature of chromium makes it a hazardous chemical and the threshold limits prescribed and recommended by the NIOSH should be implemented in every organization, farm, agricultural field and industry that indulges in manufacturing processes that involve exposure of the workers to chromium filled environment or in areas where chromium is produced as a byproduct of any metallurgical process like electroplating or manufacturing of pigments and dyes 16. Considering the adverse effects of chromium Cr (VI), a criteria document for hexavalent chromium has been developed to set an occupational exposure limit for Cr (VI) in the European Union (EU). The OEL is a health based document that contains sections on the identification of the chemical substance, its physical and the chemical properties, use and production data, recent information of the occupational exposure rates and the stats and figures for the same, the current available methods for assessment and analysis and the toxicology. The last section generally describes the criteria evaluation of data on both the humans as well as on the animals. It is important for every organization to follow the REL for exposure of their employees to Cr(VI) compounds and prevent the prevailing risk of health problems that can serve as the long term complications17.
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