Causes and effects of Water pollution Water pollution is mainly affected by human activities. For instance, industrial, domestic, and agricultural activities will produce waste which will pollute the water. First and foremost, agricultural run offs and waste from oil palm and rubber processing mills is one of the causes of water pollution. Normally, as farmers apply fertilisers on the plants, the excess fertilisers that are not assimilated into the soil will be easily wash away by rain water. Therefore, the moving rain water will bring the dissolved fertilisers to the nearby river, lake or ocean. As fertilizers are rich in nitrates and phosphorus, the excess nutrients in the lake will lead to rapid growth of algae, later causes eutrophication to happen. Besides that, there are also some herbicide and pesticide residues which will also be carried by the soil water or rain water to the nearby river. The accumulation of pesticides and herbicides may have toxic effects on organisms in the water and humans if the water is used as drinking water. Later, the pesticide levels will accumulate as they pass through the food chains. Therefore, when it reaches the final consumers which are mainly carnivores, the high concentration of pesticides accumulate in the tissues may affect their metabolism or even kill the carnivores. Studies have also shown that pesticides have led to decreased ovulation, lower sperm counts, or even the inability to conceive and birth defects. In addition, untreated sewage consisting mainly of human faeces and domestic waste is one of the causes of water pollution too. This is because the suspended solids will directly reduce the light penetration, causing a decreasing in the rate of photosynthesis for the photolytic aquatic plants. Not only that, most of the suspended solids are biodegradable. As such, they will stimulate the microorganisms to carry out decomposition, which requires a high demand of oxygen. Consequently, the Biochemical oxygen demand (B.O.D) wil increase, indicating a higher water pollution level. Moreover, domestic waste is also one of the water pollutants. For instance, detergents and food waste. There are two types of detergents, which are hard detergents and soft detergents. Hard detergents will create foam which reduces the supply of oxygen to organisms living in the water. On the contrary, soft detergents are biodegradable. However, they may contain high levels of phosphates which can lead to eutrophication. Furthermore, animal waste from farms is also considered as one of the water pollutants. This is because animal waste that are biodegradable will act as a food source for microorganisms that live in the water. Microorganisms tends to decompose them and take them as a food source. As a result, the number of microorganisms living in the water such as bacteria and protozoa will increase. If the water is used for drinking, the water that is not treated properly may cause water-borne diseases such as cholera. Next, the effluents from industries are also a contributor to water pollution. There are many industries which will release water pollutants such as food and beverage processing industry, electronics and electroplating plants, and rubber product processing industry. If the waste water that are released from the industry is not purified properly, heavy metals such as mercury, zinc and chromium that are in the water content will cause a severe water degradation. Highly toxic can accumulate in the organisms via food chains, causing death to the final consumer. Besides that, heavy metal such as mercury is very poisonous as it can cause acute nervous disorders in humans.