Risk Assessment and Epidemiology - Assignment Example

Uncertainty and variability in risk assessment of PGDN Risk assessment is the process of identifying the level of danger, due to certain human activities or nature, to the living beings. In many parts of the world, the use of specific chemicals or specific activities is not allowed unless or otherwise it is proved that it does not create illness above a specific limit. The limits are very important when risk assessment is done for chemicals. The chemicals which are proved to be safe at certain limits provide no assurance of 100% safety to the people. The main reason for this is that people vary in their sensitivity to chemical agents. The level which was declared as safe for some section of people can be a lethal dose for other sections of people. Hence for the studies based on human health effects, the data’s regarding the high dose level and low dose level should be delivered. “Uncertainty” denotes the ignorance of the actual values of the measured quantity. “Variability“ helps to describe the measurable quantities that cannot be characterized by a single value. The uncertainty and the variability for a chemical hazard is very large nowadays. The permissible limits at certain areas are hard to predict. This variability results in uncertainty. The drinking water toxological profile summarizes the information on the effect of Dipropylene glycol 1,2-dinitrate(PGDN), a volatile torpedo propellant, which is the major component of Otto Fuel II. (75% dipropylene glycol 1,2-dinitrate). Low concentration of this chemical PGDN is found in the waste waters of effluent. This effluent when mixes with the drinking water may cause severe damage to the cardio vascular and nervous system. The increased risk of angina pectoris and myocardial infarction were found among the PGDN exposed individuals Dipropylene glycol 1, 2-dinitrate enters the blood stream when we drink the water or eat the food, which is contaminated with this chemical. But fortunately the chemical will break down to simpler products in the blood stream with in 24 hours. The common health effects are headache, loss of balance, nausea, dizziness and eye irritation etc. When the exposure level is 0.2 ppm per day then it has less effect on the human. When we are exposed to 0.2 ppm for several hours the severe headache is the side effect. The headache however subsides after 8 hours. (atsdr.cdc.gov). If the concentration of the chemical is greater than 0.5 ppm and if the people are exposed to it for several hours or even several days, then it may lead to Methemoglobin. Uncertainty and variability issues for human: The PGDN which is a major component of Otto Fuel II was primarily released in water through the waste water streams. The primary data identified states that it is removed from the water through volatilization. Though it is highly soluble in water, it is completely removed from the water in few days. Propylene glycol dinitrate is easily photo oxidised and photolyzed in water. So the people who are working on the fuelling station and those who are near the Otto Fuel factories and areas are high at risk. The compound due to its volatile nature will vaporise and escape in to the atmosphere. When the people are exposed to this vapour at a concentration of 0.2 ppm for 3 hours, complaints like irritation of the eye, severe headache, nausea , vomiting are observed in them. So to ensure a safe drinking water free from the PGDN, the following efforts can be taken: The drinking water can be exposed to UV light for few hours before human consumption. The water can be kept aside for atmospheric exposure so that the volatile compounds that are present in the water will vaporise ensuring zero volatile compounds in the water. This was proved by a test. When the water containing propylene glycol dinitrate was exposed to air, 96% of the PGDN gets decomposed in 42 hours compared to 57% decomposition when kept in a dark enclosure. Similarly the decomposition of propylene glycol dinitrate was greater than 89% in nitrogen compared to 9.5% in darker enclosure. The propylene glycol dinitrate containing water can be treated with the microbial population for biodegradation of the compound. The use of fresh activated sludge as inoculant for the PGDN contaminated water at batch, and continuous culture revealed the evidence of the biodegradation of the compound. The sequential removal of the nitrate from PGDN was observed. Till now there is no evidence of water contamination of PGDN in river water. Thus PGDN proves no threat to the safety of the drinking water. If the concentration of the propylene glycol dinitrate is high then the use of activated charcoal will reduce the contaminants and also heavy diluting with water will reduce the hazard level of PGDN. (Leikin, 2007). Uncertainty and variability issues for animals: The laboratory animals are artificially introduced to propylene glycol dinitrate. The effect of this chemical on animals were studied and the results are used as an evidence for further studies. As Proctor (2004) states continuous 90 day study was done on rats, guinea pigs, monkeys and dogs. At 10 ppm, the dogs had hemosiderin deposits in liver and kidney. Pulmonary haemorrhage was observed in guinea pigs for an exposure of 15 ppm, whereas monkeys had increased serum urea nitrogen and decreased alkaline phosphatase indicating renal damage. At 35 ppm, the deposits of dipropylene glycol dinitrate were found in liver, spleen, kidney of all the animals. Methemoglobin peaked in all the cases. So to reduce these effects safety measures must be taken. A few suggestions are: The use of commercially available absorbents to absorb PGDN can be practiced. The absorbents such as pyrolyzed resins, reticulated resins and activated charcoal can be used to absorb the PGDN from the water before using it for commercial purpose (cameochemicals.noaa.gov). The grazing animals can be prevented from grazing in the Otto fuel spillage, effluent and refuelling areas. Uncertainty and Variability of risk assessment for PGDN: If I am a risk assessor, I will communicate the following points as areas of concern to the risk manager. PGDN is a potent vasodilator. It reduces the blood pressure to the least level and it lasts for hours. Apart from that it is a strong oxidizing agent too. The exposure routes are inhalation, ingestion, skin absorption and skin eye contact. (cameochemicals.noaa.gov). So the people must be kept away from this exposure. The people must be advised to wear clothes that cover 100% of the whole body. The use of breathing instruments is also recommended. The biodegradation of PGDN is the most cost effective and the best way. Hence the effluents from the Otto fuel II industries should be first stored in a pond. As the pond is the best area of exposure to sunlight for oxidation of the compound and also for biological degradation, it is the best option. The use of absorbents such as activated charcoal can be used at the effluent region of the Otto refuelling industries to absorb the compound ensuring zero contamination. Understanding of uncertainty and variability: The use of hazardous chemicals or specific hazardous activities is not allowed in many countries without intense research, due to the uncertainty and variability effects of the chemicals to human beings. The human beings vary in their sensitivity, exposure level, and immunological level to those chemicals. So there is no guaranty that the same standards can be common for all the regions of the world. For example, the use of B-complex tablet is the best cure for many people whereas the same complex is a lethal one for certain individuals due to their varying environment. Hence the understanding of the potential risk of PGDN will help us to overcome the harmful effects of this chemical and to use it in a proper way. References: atsdr.cdc.gov. (1995). Toxicological Profile for Otto fuel II and its components. Agency for toxic substances and Disease Registry. Retrieved June 29, 2009 from http://www.atsdr.cdc.gov/toxprofiles/tp77.pdf cameochemicals.noaa.gov. Propylene Glycol Dinitrate, Chemical Data Fact Sheet. Retrieved June 29, 2009 from http://cameochemicals.noaa.gov/chemical/25057 Leikin B.J. and Paloucek F.P. (2007).Poisoning and Toxicology handbook. Informa health care publishers. Proctor, N.H. and Hathaway, G.J. (2004). Proctor and Hughes’ Chemical Hazards of the work place, 5th Edition. Wiley IEEE publishers. Read More