For calculating Chronic daily intake (CDI) of carcinogenic metals in drinking water samples near to a landfill site only 2 years old... thus, the exposure duration (ED) is 2 years So, what will be "Average time of exposure" (AT)?
Yes!
That's what i think...
But can understand the logic behind multiplying by 365 days...
Doesn't it alter the actual CDI?
Hi Anum,
Do you mean the land fill existed for only two years? Or the individuals are exposed for only two years? Remember that in risk assessment your assumptions must be clear and justifiable. Because exposure duration varies for either carcinogenic or non-carcinogenic.
Average time (AT) is the period over which exposure of an individual to the pollutants/metal is averaged and is given in days. For carcinogenic risk estimation, the lifetime expectancy is considered as your exposure duration (ED). AT is calculated below;
AT = Lifetime (70 years) x 365 days per year
Chronic daily intake (CDI) is also called the lifetime average daily dose (LADD). The lifetime expectancy of 70 years is usually used. But i advice you to get the actual lifetime expectancy of the people in the "study area" so that you have a correct and precise risk estimation.
For non-carcinogens risk, AT = ED x 365 days per year.
Best of luck.
Hi Isa..
Thanku for explaining...
What i mean is that its been only two years since that landfill started its operation there and is expected to reach its limit in 2026. the community was living there before the landfill.
so in this case, so i still need to average lifetime expectancy? or just the actual exposure duration?
Hi Anum,
OK. I get your point clearly. But even if the landfill reach its limit by 2026 (In the next 8 years), the pollutants may still be in the surrounding environment for a long period of time especially considering the persistent nature of heavy metals. Therefore the exposure will still manifest. I advice that you based your assumptions on the probability of an individual whether adult or children to be exposed to cancer threat within the life expectancy period. This is for the risk estimation.
On the issue of the community drinking metals in the contaminated water, you can relate your experimental results to the metal permissible limits/reference limits in raw or drinking water, and by using calculations such as metal pollution index etc.
You can refer to the following articles for more information on risk estimation in drinking water;
Article Health Risk Assessment of Heavy Metals and Their Source Appo...
Article Health Risk Assessment of Metals in Surface Water from Fresh...
Article Cancer and Non-Cancer Risk Assessment from Exposure to Arsen...
Health risks associated with heavy metals in the drinking water of Swat, northern Pakistan
Best of luck.
AT = Averaging Time (period over which exposure is averaged) (days)
For noncarcinogens: AT = ED * 365 days per year and intake is called Chronic Daily Intake (CDI).
For carcinogens: AT = Lifetime (70 years) * 365 days per year and intake is called Lifetime Average Daily Dose (LADD).
Best of luck.