Toxicity of Diesel Particulate Matter Particulate and Mercury Hg - Essay Example

Overview of the Toxi of Diesel Particulate Matter (DPM) particulate and Mercury Hg (Vapour) Introduction Working people spend nearly 90% of their time indoors. This emphasizes the significance of promoting high air quality in modern work environments. However, concerns on air pollution are an in thing both at work and home. While individuals are responsible for air quality control at homes, this responsibility shifts to the employer within the workplace. Given that air quality not only affects employees’ productivity but also availability, many employers are keen to develop clean work environments. This paper identifies two workplace air contaminants and analysis their sources, applicable exposure limit, toxico-kinetics and toxico-dynamics. The two are Mercury (Hg) and Diesel Particulate Matter (DPM). 2. Sources of Exposure 2.1. Diesel Particulate Matter This is a component of diesel exhaust (DE) and encompasses soot particles. The primary components in soot particles are carbon, sulphates, metallic abrasion particles, silicates, and ash. While carbon forms the solid core in soot particles, all other components are attached to its surface. The surface of the carbon core also has attached to it the aromatic hydrocarbons which are organic carbon compounds (Sheesley, et al., 2008, pp. 306-307). DPM particles have varying sizes ranging from fine to ultrafine particles that are emitted from a wide range of diesel engine sources. Common diesel engines in the workplace include road diesel engines of trucks, cars, buses of the road diesel engines like heavy duty equipment, marine vessels and locomotives. Additionally, the employees mostly at risk of exposures in the workplace include truck drivers, miners, miners, toll booth workers, forklift drivers, dock workers, mechanics and garage workers, and farm workers exposed to diesel exhaust (Sheesley, et al., 2008). Mostly, the exposure pathway to DPM is inhaling air containing diesel particulate matter. Breathing air containing fine and ultrafine particles is possible since they are respirable hence rendering them harmless and making them undetectable by the defence mechanisms in the human respiratory system. Consequently, the particles get deep into the lung and the exposed persons experience lung inflammation and alterations in lung cells as well as immunological effects. In severe cases, Sheesley, et al (2008, p. 311)occupational environments experience elevated rates of lung cancer since DPM is suspected to have carcinogenic effects. In acute exposure instances, employees experience irritations in the nose, eyes, lungs, and throat, and light-headedness, nausea, cough, and worsened asthma. 2.2. Mercury as Hg (Vapour) Despite the fact that many people have mercury in their bodies, lower than the levels linked to possible health effects, nearly everyone has trace levels of methyl mercury in their bodies (Bernhoft, 2012). Mercury emissions into the environment include manufacturing and coal burning for fuel. In addition, mercury enters the environment due to volcanic activity that also causes environmental mercury to rise. However, human sources of mercury are estimated to range from one third to two third of the entire mercury releases. Although not all levels of mercury in the atmosphere results to health risks, continued mercury production from human activities result to accumulation of up-to about 80% from smelting, mining, and combustion of fossil fuels. Other sources include industrial waste water accounting for about 5%, municipal solid waste from discarded thermometers, electrical switches, fungicides, batteries. The most common form of environmentally available mercury is metallic and inorganic. Some common work environments with mercury are plants fired by coal, mercury-ore mining sites, incinerators where medical and municipal wastes are burned, cement producing plants, and mercury linked factories with unregulated releases. Incineration of municipal wastes involves garbage in form of fluorescent light bulbs, electrical switches, thermometers, or batteries. Organic mercury compounds are released into the soil or water through the use of fungicides with mercury. Additionally, humans are exposed to mercury vapour from dental amalgam resulting to sufficiently adverse health effects especially on sensitive populations such as pregnant women, persons with impaired kidney functions, children below 6 years, and persons with hypersensitive immune response to metals (Bernhoft, 2012). Most instances of employees’ exposure arise from breathing mercury contaminated air. Some occupations at high risk exposure include dentists and their assistants, chemical processing plants, electrical equipment manufacturers, chemical processing plants, manufacturers, and family members of such workers. 3. Applicable Occupational Exposure Limits (OELs/ PELs) 3.1. Diesel Particulate Matter DPM For Singapore, the most crucial air pollutant is particulate matter (PM). Singapore’s ambient concentrations of pollutants compare to the US EPA guidelines to identify the crucial pollutants as having diameter not greater than 2.5 micrometres. This pollutant is relatively low in concentrations. Permissible exposure levels (PEL) for over 600 toxic substances include both long term and short term. PEL (Long Term) refers to permissible exposure amount above an 8-hour working day and 40-hour working week (Ministry of manpower, 2013). PEL (Short term) refers to exposure extents above 15 minutes duration for a working day. DPM is a suspect carcinogen responsible for lung cancer in severe exposure conditions. 3.2. Mercury as Hg (vapour) or (CAS Reg. No. 7439-97-6) In Singapore, the Safety and health of workers is protected by the workplace Safety and Health WSH Act. The WSH Act aims at cultivating proper safety and health practices and habits for all persons in the workplace. In the workplace, exposure to mercury vapour is only applicable either as Time Weighted Average (TWA) of 8-hours limit. TWA exposure limit has units in milligrams per meter cubed (mg/m3). The exposure limit to liquid mercury is given in Short Term Exposure Limit (STEL) and uses mg/m3 units like TWA. The applicable exposure limits for mercury vapour in workplaces in Singapore are summarized below. Substance [CAS No.] TWA STEL/Ceiling Notations Mercury Methly as Hg[7439-97-6] 0.01mg/m3 0.03mg/m3 Skin 2B Figure 1: Summary of exposure limits for Mercury vapour. Source: (World Health Organization, 2011) 4. Toxico-Kinetics 4.1. DPM The largest component of DPM is polynuclear aromatic hydrocarbons. thus forming a complicated aerosol system. DPMs, inhalation results to deposition on airways surfaces while gaseous aerosols are exhaled. The deposition of inhaled particles is dependent on particle aerodynamic size where >10 micrometre are deposited in the extrathoracic section of the respiratory track while particles with main proportion of 5-10 micrometre are deposited in larger conductive airways just close to the bronchioles or fine airways. These patterns are observable with nose breathing. However, mouth breathing results to reduction in extrathoracic deposition and increased pulmonary and tracheobronchial deposition. Particles deposited at the extrathoracic region are 7 to 15 micrometre as opposed to 3 to 5 micrometre for the tracheobronchial and pulmonary regions. For particles to be deposited in the lungs, the main factors include particle characteristics, breathing pattern and tidal volume, and anatomy of the respiratory track. 4.2. Mercury vapour Hg0 Despite being a toxic heavy metal, exposure to mercury has been experienced in public health disasters in places like Japan, Minamata Bay, and Iraq. Hg0 is absorbed with ease through the mucus membrane after inhalation. The vapour then moves to the lungs where it is swiftly oxidized to other types. However, oxidation rate is not fast enough to avert substantial deposition of elemental mercury in the human brain. Upon entering the human body, mercury vapour has very high affinity for sulfhydryl groups thus bonds to sulphur-containing amino acids in the whole body. It is then that it is transported to the brain and dissolves in serum or adheres to the membranes of red blood cells. Metallic mercury vapour, like metallic mercury is expelled as mercuric mercury. However, the excretory half-life varies broadly based on deposition organ and redox state. 5. Toxico-Dynamics 5.1. DPM Exposure to DPM affects the immune system through alterations of processes such as recognition, cellular proliferation, clonal expansion, migration, and apoptosis. Since DPM is suspect carcinogen, chronic exposure results to increased vulnerability to infectious cancer, asthma, infectious disease, and types of autoimmune diseases. Furthermore, both outdoor and indoor air pollution from diesel particulate matter (World Health Organization, 2011, p. 23) results to exacerbation of asthma or respiratory diseases. 5.2. Mercury Vapour Hg0 After short or prolonged accumulation in the body, mercury in all forms results to potential impairment of the functioning of the affected organ or the structure of any sub cells (Bernhoft, 2012). As of mercury vapour, the main targets include brain, as well as other peripheral nerve function, immune function, renal function, muscle and endocrine function, and other forms of dermatitis. In the case of intense acute exposure, victims experience erosive bronchitis and bronchiolitis that result to respiratory failure. Respiratory failure may be accompanied by Central Nervous system symptom like erethism or tremor. Conversely, chronic mercury vapour exposure results to dysfunctional neurological system. Advanced exposure levels are linked to mercurial tremor causing fasciculation of fine muscles characterized by coarse shaking. Other outcomes of high level exposure include memory loss, fatigue, depression, severe personality and behaviour changes, and hallucination and delirium. However, on low level of chronic exposure, symptoms include anorexia, fatigue, weakness, gastrointestinal disturbance, and weight loss (Bernhoft, 2012). 6. Conclusion Whether indoor or outdoor, exposure to lethal substances such as mercury vapour and DPM should be controlled. This is a crucial way of ensuring that employees work under necessary protective clothing. Additionally, adherence to workplace safety and health standards result to productive employees, and lesser vulnerability to lung cancer due to prolonged diesel particulate matter exposure or brain damage from chronic mercury vapour exposure. Bibliography Bernhoft, R. A., 2012. Mercury Toxicity and Treatment: A Review of the Literature. Journal of Environmental and Public Health, 2012(460508), p. 10. Ministry of manpower, 2013. Guidelines on Prevention and Control of Chemical Hazard, Sigapore: Ministry of Manpower. Sheesley, R. et al., 2008. Assessment of diesel particulate matter exposure in the workplace: freight terminals. Journal of Environmental Authority Manuscript, 10(3), pp. 305-314. World Health Organization, 2011. Summary of Principles for Evaluating Health Risks In Children Associated with Exposure to Chemicals, Geneva: World Health Organization . Read More