Read this article to learn about the effects of radiation on plants and animals.
Effects of Radiation on Plants:
According to the Health Physics Society radiations have a positive effect on plant growth at lower radiation levels and harmful effects at high levels. Plants need some types of non-ionizing radiation like sun-light for photosynthesis. Though these solar radiations are vital for the survival of plants but some other forms of non-ionizing and ionizing radiations are deleterious for plants.
Ultraviolet radiation affects plant growth and sprouting and the amount of damage is proportional to the radiation received. Due to radiation exposure soil can become compact and lose the nutrients needed for plants to grow. The experiments conducted in laboratories by supplying ultraviolet radiation through filtered lamps proved that higher doses of radiation administered to the plants were highly damaging.
Radiations disrupt the stomatal resistance. The stomata are a small air hole within the plant leaf that also controls water levels. If there is too much evaporation due to intense radiation the stomata close to reserve water. If the stomata are unable to open for a long period of time, the growth of the plant is stunted. Prolonged exposure to radiation can completely damage the stomata and ultimately the plant is destroyed.
Plant cells, contain chromosomes i.e. the genetic material responsible for plant reproduction if the ceil is much damaged by radiation then reproduction is hindered. As UV radiations destroy cells, the chances of mutation are increased. Affected plants are often small and weak with altered leaf patterns.
Prolonged radiation exposure can completely destroy the fertility of plant and the plant gradually dies. The surroundings also become poisoneel and may prevent the growth of future offspring’s. Studies have revealed that after the disastrous Chernobyl accident the herbs, plants and soil of Sweden and Norway were showered with radioactive rain for many days which entered the food chain through soil and ultimately to human body. Even today the lichens people eat are contaminated with radionuclides. Radionuclides also increase the rate of mutation in plants Radioactive elements tend to accumulate in soil sediments, air and water and ultimately they reach man.
Intense radiations kill plants but differently. Trees and shrubs vary in their reactivity and sensitivity towards radioactive substances. This variation is found mainly due to the difference in their size and chromosome number. Sparrow had reported that plants with less number of chromosomes offer larger target of radiation attack than those with excess of small chromosomes.
According to one report of 1990 each tonne of phosphatic fertilizer contains 82 kg of fluorine and 290 micrograms of uranium, which severely pollute the soil and plants. In coastal Kerala between Charava and Neendakara soil contains monazite having radioactive element thorium. Due to this the terrestrial radiation in this area is very high i.e. 1500-3000 milliroentgens (mr) per year. In Kerala frequency of occurrence of Downs syndrome is also quite high.
According to a survey of all India Institute of Medical Sciences (AIIMS) in a high exposed group in Kerala, high prevalence of mental retardation and Downs syndrome was noticed. The prevalence of Down’s syndrome was 0.93 in 1000. The scientists speculate that the radiation accelerates the aging of egg cells and causes primary trisomdy. Down’s syndrome frequency in offspring’s increases with the age of mother. The highest frequency occurs in offspring’s of women in the age group of 30-40 i.e. 1: 81.
The table below depicts the frequency of Down’s syndrome in some countries:
According to one report of University of Southern California due to the Chernobyl accident huge radiation pollution occurred in the surrounding area and along with human population and animal, plants were also badly affected.
Some plants such as pine trees died immediately. Radiation pollution is comparatively high near nuclear power plants and many radionuclides especially caesium 137, iodine 131, strontium 90 and carbon-14 occur in abundance there which accumulate in plant tissues growing in that region. Plants absorb maximum light near 280 nm, due to this reason plant proteins are more susceptible to ultraviolet radiations.
In plants 20 to 50% reduction in chlorophyll content and harmful mutations are seen due to UV radiations. A report from Australian National University suggests that UV-B (i.e. UV- Biological) radiations reduce the effectiveness of plant photosynthesis in plants by up to 70%. Due to intense UV radiations greater evaporation of surface water occurs through the stomata of the leaves which results in decrease in soil moisture content.
Many marine algae and other sea weeds accumulate high concentration of radioneuclides in their body. Sea weed Sargassam contains high concentration of Iodine-131. Manganese 54 (Mn-54) is also accumulated in algae and other marine organisms. Zirconium 95 (Zr-95) is absorbed by algae Ce-141 is mainly found in algae inhabiting the seashores. Similarly many other radionuiclides also get accumulated in different sea weeds and algae and ultimately reach human beings through sea foods.
Effects of Radiation on Animals:
Biological effects of radiation are generally common to man and animals. Higher animals are more susceptible to genetic damages due to radiation. Exposure is high in higher animals than the lower animals such as flies and insects. Studies on Drosophila have shown that mutation rates were increased enormously on radiation exposure.
After the Chernobyl accident in Soviet Ukraine high levels of cesium-137 and iodine-131 accumulation were reported in reindeer herds of Sweden and Norway. Ce-137 and I-131 accumulate severely in plant and animal tissues. Many Rodents die immediately after leakage. Commissioning of Boiling Water Power Reactor (BWRS) in USA, Europe and India and other countries have enormously polluted the environment.
Even the small amount of radionuclides may lead to an increase in mutation rate in animals. Lethal doses of fall out radiations reach catties through grazing on polluted lands. The radionuclides enter the metabolic cycle and thereby incorporate into DNA molecules in animal cells causing genetic damage. Radiations generally induce ionizing and photochemical reactions and thereby incorporate into DNA molecules in animal cells causing genetic damage.
Because of the high costs of chemical reprocessing some amount of nuclear waste material is customarily released into the sea. In the West Coast of Britain, the following isotopes have been released over the past thirty years. The important isotopes in the discharge include Zr95, Nb95, Ru106, Cs137Ce144, Pu238, Pu239 and Pu240 In USA, eight nuclear plants are located along the bank of lake Michigan and Hudson River. Due to this reason large number of long lived radionuclides is found in these waters making it poisonous for aquatic animals and fishes.
Though the radioactive wastes are diluted and packed into sturdy containers before releasing them into sea, but still many marine animals absorb them selectively. The radioisotopes of cesium, zinc, copper and cobalt are accumulated in the soft tissues of these animals but those of radon, crypton and calcium are found in bones. Seaweeds concentrate cobalt and Iodine. Sea-weed Porphyra used to prepare bread is UK was found contaminated with radioactive ruthenium (Ru106).
It is also reported from crab muscles and fish tissues. Mytilus edulis accumulated 95% of Ru106 in its shell. Similarly radionuclide Iodine -131 is found accumulated in marine organisms. Strontium (Sr-90 and Sr-89) is found in high proportions in shells of molluscs, crustaceans and bones of fishes, Cs-137 is found mainly in crustacean shells. Concentratem of Cs-137 in crabs shell is 50%, in its muscles it is 22% and in liver and other tissues the concentration of Cs-137 is 10%.
Zinc-65 (Zn-65) is found in liver, spleen and gills of various fishes. Manganese (Mn-54) is also found in high concentration in mollusks, benthic organism, oysters and algae. Phosphorus (P-33) is found in significant amounts in fish tissues. Salmon fish, sawry fish and tuna show high concentration of Iron (Fe-56).
Similarly many other radionuclides like Ce-141, Zr-96, Co-60 are reported from aquatic animals and all these harmful radionuclides besides causing hazardous effects in these organisms also reach the ultimate consumer i.e. Man through the food chain and cause severe health hazards due to disruption of metabolic changes and physiological processes. Radiation exposure due to radiation therapy also has some harmful effects.
With advancement in veterinary medicine radiation therapy is increasingly being used to treat cancer in animals. Radiation can affect normal and cancer cells but localised X-ray can cure or control tumors that may not be killed by surgery or chemotherapy alone. In animals also cancer works much the same way as it does in man.
Dysfunctional cells begin to over-multiply and this growth causes them to destroy healthy cells around them. Animals normally receive 2-5 weeks treatment. Side effects of radiation therapy occur within 3 months after discontinuing the treatment and include dryness and itching in skin, alopeciasor hair loss and hyper-pigmentation of skin around the tumor site.
If tumor is in nasal or oral region then mucosal areas of nose and mouth may become inflamed and irritated. In addition to this, the tumors often release an unpleasant odour as the cancerous cells die. More serious side effects may include some nerve damage and either the death or hardening of healthy tissues i.e., fibrosis. While most of these conditions are temporary but skin discoloration and hair loss is often permanent.