That's how people misread technical reports. It says:

There are known biological effects at levels WELL ABOVE 100uT.
The average exposure being above 0.3uT is rare.
The level DIRECTLY below power lines can be 20uT.

So far so good: even below power lines the level is well below that known to cause harm.

Then it says:

Childhood leukemia is rare (about 49000 cases; the child population of the world is perhaps 1 billion, most of whom live in areas with electric power).
1-4% of children live in fields greater than the average 0.3uT field.
The number of cases that MIGHT be attribuyed to ELF is 100-2400 (in a population of 1 billion)
A (disputed) study suggested that this (small) possibility might be doubled from tiny (1 in 400000) to slightly less tiny (1 in 200000).

Compare the 2400 worldwide cases with 5000 children killed/ seriously injured in traffic accidents in the UK in 2001 -child population 1 million- a thousand times the risk.

Note that it does NOT say that these children live in areas of 0.3-0.4uT- it is above this, and it doesn't say how much above. The dispute about the study cited is stated to be partly procedura, but in all epidemiological cases there is the problem of detecting effects that are well down in the "noise".

And note what I said previously: if you have electricity, you EITHER have pylon lines with high electric, but low magnetic, fields; or underground lines with low electric, but high magnetic, fields. The alternative is no electricity.

And I suspect Guest Guest Housebuyer isn't a child (though s/he might have them).