replacing numbers in LARGE MATRIX with criterium in 2 columns (a--> b)

[Alexzive]

Hello,
I have this matrix [20*4 - but it could be n*4 , with n~100,000] in
file "EL_list" like this:

    1,      1,      2,      3
     2,      4,      1,      5
     3,      5,      1,      6
     4,      7,      5,      6
     5,      8,      7,      9
     6,      8,      5,      7
     7,     10,      9,      7
     8,     10,     11,     12
     9,      7,     13,     10
    10,     14,     15,     16
    11,     14,     17,     15
    12,     17,     14,     18
    13,     13,     16,     10
    14,     16,     15,     11
    15,     16,     11,     10
    16,     19,     20,     21
    17,     22,     15,     20
    18,     17,     20,     15
    19,     23,     20,     24
    20,     25,     24,     20

I would like to replace some numbers in "EL_list" but only in columns
2,3,4 using the criterium by line in file "criterium" (column 1 are
the new numbers, column 2 the old ones).

1	1
2	3
3	5
4	12
5	13
6	14
7	15
8	16
9	17
10	18
11	19
12	10
13	21
14	22
15	23
16	24
17	25

For example all the 7 have to replaced by 15 and so on..

-- How to implement it in a fast end efficient code?

many thanks, Alex