View report page

APPENDIX VII
From Where does Leaf Assimilate the
Deadly Cumulative Poison of Lead?
SOME apprehension seems to be
felt about the new Lead in Food
Regulations which come into
force on April 16. Indeed, the Mail last
week went so far as to say that by
forbidding the use of tea containing
more than 10 parts per million of lead,
the Regulations would place an unfair
imposition on the trade and be likely
to result in imports of Formosa tea
into the United Kingdom becoming
negligible.
But are not such comments more
unfair than the Regulations, which only
seek to protect the public from a
particularly insidious and cumulative
poison? They could be most damaging
to the reputation of Formosa tea, most
of which, to judge from hundreds of
analyses, contains hardly any more lead
than Indian, Ceylon or African tea.
Some fine teas have come from Formosa
in the past and there is no reason why
they should not be equally welcome in
the future.
To bring into perspective the potential
interference to the tea trade, the
reports of the Port and City of London
Health Authorities for 1960, the latest
published, show that of the 3,191
samples of tea analysed only 20 or 0.6%
were found to contain lead in excess of
10 parts per million. Since samples
submitted for analysis have already been
seeded to some extent by the Sampling
Officers this percentage is biassed and
the true proportion of the total tea
imports containing excessive lead would
probably be much lower. Furthermore,
the samples reported against were not
all Formosa but included teas from two
other countries.
Where there may be any reason to
suspect that any kind of food might
contravine the Food & Drugs Act or
any Regulations made under it, two
precautions can be taken by the
importers: (1) to insist upon a protective
clause in their contract providing for
cancellation if the food is stopped by a
Port Health Authority, and (2) to
obtain a sample of each invoice and
have it tested before confirming the
order. To be on the safe side, any
teas showing a lead content exceeding
6 parts per million should be avoided,
or at best, accepted with reservations.
To an outside observer it seems surprising
that the recent consignments of
Formosan tea, which entailed considerable
losses to the importers concerned,
were apparently accepted without such
precautions, although it had been known
for two years that high leads had been
found in similar grades of tea.
Lead Foil Abandoned
But the most obvious step, when any
undesirable substance is found in food,
is surely to find out how it gets in. This
is not the first time lead has been found
in tea and the trade will recollect that
high proportions were found some 25
years ago. The lead was then found to
be due to abrasion of the lead liners of
the chests. The use of lead foil was
discontinued and the trouble ceased.
A few more sporadic cases have since
occurred, which it is understood were
raced to the use of solder for repairing
worn machinery and to the flaking of
dilapidated lead paint in certain
factories.
Lead is of course not the only harmful
impurity that can find its way into tea.
Nor is tea the only food in which it has
been found. Outbreaks of lead poisoning
in this country have occurred from
the consumption of cider and beer
containing 1 to 2 parts per million of
lead derived from lead arsenate spraying
and from the use of lead piping, now
believed to have been completely
eliminated. In the peasant village of
Sopic in Serbia an epidemic of severe
nephritis with 37 deaths, has recently
been traced to the use of flour containing
1 to 2 parts per million of lead, deriving
from an old stone water mill, the pitted
surfaces of which had been repaired
with compounds of lead. In Rotherham
in 1955 an outbreak occurred affecting
60 children, with 2 deaths, in some
poorer class houses, which was traced
to lead-containing dust from discarded
battery casings which had been used as
a cheap fuel. In certain parts of
Queensland, where exposure to lead
appears to be abnormal, poisoning has
occurred and subsequent records of 165
children discharged from hospital as
cured showed that 94 died of chronic
nephritis 15 to 20 years later. In
America, in particular, recent investigations
have shown that serious and
permanent mental retardation can result
from lead encephalopathy in young
children afflicted by the habit of
chewing anything within reach, traces
of lead being derived from the paint.
Many other instances of lead poisoning
have also been recorded and from the
accumulated medical and analytical
evidence it has been possible to deduce
the maximum safe limits for various
foods.
Narrow Margin
The real trouble with lead is that it is
cumulative, and that there is such a
small margin of safety between the
average amount we ingest from food,
drink and the atmosphere everyday and
the amount which the body can eliminate.
This margin, culled from 40
investigations, appears to be as little as
half a milligram a day, or a hundredth
of a grain; if we take more than that it
becomes deposited in the bones and after
a time a point is reached when the
skeleton will absorb no more and,
influenced by health, diet and other
factors, discharges the surplus lead into
the blood stream, where it is carried to
susceptible organs causing the outward
symptoms of lead poisoning. For this
very reason a heavy dose of a lead compound,
most of which might pass
undissolved through the body, is less to
be feared than minute but repeated
doses which, added to other past and
future doses, could produce a chronic
toxicosis years later—usually too late
for any connection to be established
with the source or for any redress by the
unfortunate consumer.
The public have the right through
their representatives to legislate to
protect their health; and certainly no
one in the tea trade would care to run
the risk of tea being responsible for, or
in any way associated with, the next
outbreak of lead poisoning. By laying
down definite limits for all foods the
Regulations will ensure that the same
standard is adopted all over the country
and enable producers to know what is
required.
The lead limit for most foods has
been fixed at 2 parts per million. For
those kinds of food and drink which are
consumed in large quantities it is lower,
—0.2 to 1 part per million; for others,
consumed in only small quantities, it
varies from 5-20 parts per million. The
design being to ensure that the probable
intake from any particular food will not
exceed \ milligram in one day. It is, of
course, to be hoped that food producers
will endeavour, as they have in the past,
to exclude lead from their products
entirely; indeed, if all the food we consumed
contained the maximum amounts
of lead to be permitted by the Regulations
it can be calculated that an
average intake would exceed 3 milligrams
a day, and we should all be
suffering from lead poisoning within
a few months.
The Regulations cannot, therefore,
be regarded as unduly severe. In the
case of tea, due allowance has been
made for the small weight normally used
per person and the assumption has also
been made that probably only about
one-third of the lead will pass into the
liquor. In view of the evidence, obtained
from thousands of analyses, that
the normal lead content of tea is from
1 to 3 parts per million and that anything
over 5 is very rare, the limit of 10
parts per million should not be difficult
to comply with. By way of comparison
the U.S.A. limit of 2.5 for lead in
imported tea may be mentioned.
The solution of the Formosa problem
is, however, one that can only be
cleared up by the producers themselves.
No plants are known to. the writer that
absorb lead compounds from the soil
through their root system and translocate
it to their leaves. It would, therefore,
seem probable that the lead is
adventitious; but whether it comes from
dust from the soil settling on the leaf,
from lead-containing insecticides, from
lead in the machinery, from paint, from
the workers or from any other souro
is a question for investigation on the
spot; and surely this would be worthwhile.
The Sardine Problem
Encouragement may perhaps be
drawn from the analogous example of
lead in sardines, which was solved in
1933. For some time excessive amounts
of lead, up to 70 and even 150 parts per
million, had been found in canned
sardines imported from Portugal. Complaints
to the producers had no effect,
but since Portuguese sardines were
preferred by many customers importers
were reluctant to discontinue theii
supplies. Eventually the directors of a
large catering firm, one of the principal
users of sardines, thought it worth
while to send one of their number, who
was also their Chief Chemist, out to
Portugal to investigate the source of the
lead. In quite a short time, Dr. L. H.