I am working on heavy metal and need to calculate THQ. Would any body help me to calculate and also tell me what is what in this formula THQ = E F x F D xDIM ∕ RfDxWxT. Is any value constant in this formula?
A method to calculate THQ experimentally is explained as:
[A] Procure vegetables from three sites ( Rural, Urban and Semi-)
[B] Classify the vegetables as root(Parsley, Carrot, Onion etc), Leafy( Cabbage,Lettuce etc ) and fruity(Cucumber, Green beans etc )
[C]* (i)For Root vegetables (Cu =1-4 mg/ Kg; Zn= 10-50 mg/ Kg; Cd = 0.1-0.27 mg/ Kg and Pb= 1-5.5 mg/ Kg fresh matter . (ii)For leafy vegetables Cu------repoted in literature),Zn=(--repoted in literature) Cd =2-10 mg/ Kg dry matter) and Pb =40-250 mg/ Kg dry matter) etc----etc.,
(iii)Fruit vegetables -Pb (0.6 mg/ Kg fresh matter) and Cd around 0.1 mg, Kg fresh matter etc ---etc (reported in literatre)
*Pls. note that are these values reported in literature for different countries. But you have to experimentallly determine the values of these metal contents in the types of vegetables you want to investigate. In the present method of calculation, I have taken the values to be the average of the two reported extremes.
[D]. Oral reference doses (RfD) (mg/ Kg/ day) for elements reported in literature:
Fe (0.700 ), Mn (0.014), Zn (0.300), Cu( 0.040), Ni (0.020) ,
Cd( 0.001), Pb (0.0035).
[E].The average body weight assumed is Wmale = 68 Kg and Wfemale = 60 Kg.
[F].THQ = EFxFDxDIM/RfDxWxT
(i) EF is exposure frequency;
(ii)FD is the exposure duration,
(iii)DIM is the daily metal ingestion (mg/ person/
day ) and is calculated as:
DIM = Daily fresh food ingestion (Kg/ person/ day)
× Metal content (mg/ Kg fresh matter).
(iv) RfD is the oral reference dose (mg/ Kg/ day)
(v)W is average body weight(Kg)
(vi) T is the average exposure timeage exposure time for noncarcinogens (365 days/ year× number of exposure years).
(vii)Here EF was setup at 122days/ year(eat each one the three kinds of vegetables on every third day)
(viii) Length of exposure (FD) was set to 65 for males and 68 for females based on the average life expectancy in India,starting from 8 years of age .
[G] In a way we should calculate Three sets of values- ONE for the MALES at Rural. Urban an Semi Places and SECOND set for FEMALES at the same places.
But due to the paucity of space/ time, I try only ONE SET for MALES and the OTHER SET for the FEMALES. So much so, I include ony TWO METALS ( the most toxic-Cd, Pb) to explain the method while the results for other metals can be calculated similarly.
[H] We assume the on the aveage MALEtakes 150g (0.15 Kg) and the FEMALE takes 120g (0.12 Kg) per day of Root, Leaffy and Fruit vegetable on every third day.
[I] MALE- (ROOT Vegetables)
THQ(Cd)=122. (68-8). 0.185. (0.15) /0.001.68.365.(68-8)=0.136
THQ(Pb)=122. (68-8). 3.25. (0.15) /0.0035.68.365.(68-8)=0.684
FEMALE- (ROOT Vegetables)
THQ(Cd)=122. (68-8). 0.185. (0.12) /0.001.68.365.(68-8)=0.0984
THQ(Pb)=122. (68-8). 3.25. (0.12) /0.0035.68.365.(68-8)=0.547.
http://link.springer.com/article/10.1186%2F1752-153X-5-64#page-1
you can download this paper
i hope it will be useful for you
Azizul Haque Md
This link could help you
https://www.researchgate.net/post/How_do_you_use_THQ_target_hazard_quotients
THQ = (EFr x ED x FIR x C / RFD x B x TA) x 10-3
Where EFr = exposure frequency to pollutant which is 365 days in a year , ED = exposure duration duringaverage lifetime which is 65 years in ,.FIR = average daily consumption of food stuff in kg for one person which is 0.07 kg. C =concentration of heavy metal in food sample in μg per g.RFD is an oral reference dose of heavy metal in μg per g in a day which are (Pb, Cd, Cu, Zn, Cr and Ni values were 0.0035, 0.001, 0.040, 0.300, 1.5 and 0.020 mg/kg/day, respectively) (USEPA IRIS, 2006), B is body weight which is 70 kg. TA is the average exposure time for non-carcinogens (ED x 365 days/year)
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