For some time now, it has been known that environmental pollutants have detrimental effects on animals and humans alike. Environmental pollutants refer to any chemical that has been introduced into the natural environment which can cause damage. They can be very dangerous to human health and persist in the environment for decades. Understanding the effects of these environmental pollutants pose to the health of companion animals, will help us ascertain the true level of danger these chemicals pose to human health. This is because companion animals intimately share the same environment as us: they share the same living space, drink the same water and to some extent share the same food as humans. Therefore, they are exposed in a very similar way to the environmental pollutants that we are also exposed to. In this post, I will primarily be discussing the environmental pollutants that affect dogs and humans in a similar way.
There are around 1,500 chemicals that are listed as dangerous to human health at the moment, and worryingly, this list is continuously growing. Some of these chemicals are included in everyday items such as insecticides, paint, fragrances, house insulation, electronics, food, fertilisers, plastics and flame retardants. A table of a few of these chemicals and the diseases which they are associated with is included in this post. As you can see from the table below, there is a wide variety of ways in which these chemicals can affect health. Because many of these diseases may not exclusively occur as a result of environmental pollutant exposure, it is really challenging to understand what amount of exposure to these chemicals is dangerous.
One of the most common diseases which can occur from environmental pollutant exposure in dogs and humans is cancer. In particular, one type of cancer which has significantly increased in incidence over the last few years in both species and has been associated numerous times with environmental pollutants, is mammary cancers (known as breast cancer in humans). Mammary cancers often arise from the disruption of oestrogen hormonal signalling, controls amongst other things cell proliferation. Chemicals such as pyrethroids (found in household insecticides) are able to hijack oestrogen signalling in mammary tissue. Pyrethroids are able to enter living organisms by being inhaled, ingested or absorbed through the skin. Once inside, these chemicals preferentially migrate to bodily tissues with high a fat content, such as around the mammary gland. At the molecular level, pyrethroids look structurally very similar to oestrogen and therefore are able to “switch on” cell proliferation in the local area. This prolonged activation of oestrogen signalling ultimately results in the growth of a tumour which then becomes cancerous.
While it is worrying that pollutants found in the environment can lead to deadly diseases such as mammary cancer, companion animals have enabled scientists to make significant advancements in understanding the health hazards that environmental chemicals pose to human health. Even so, it is evident that more research into this area is needed to understand what exposure levels to these chemicals are dangerous and whether the implementation of more rigorous environmental protocols is necessary.
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