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Pesticides in celery

By Alison White

Non-organic celery, like other salad vegetables, tends to be heavily sprayed. Recent analysis of pesticide residues revealed as many as 14 different pesticides in just 10 samples of celery, and all samples had detectable residues in them.

Data analysed comes from the Food Safety Authoritys first and third quarterly reports of the Total Diet Survey released this year and also from Soil and Health testing of celery samples this year and in 2002.

Two residues of particular concern were the fungicides chlorothalonil, found in nine of the ten samples, and the dithiocarbamates, found in six out of eight samples analysed.

Chlorothalonil is bad news both for human health and the environment. It is labelled a probable human carcinogen by the EPA. It has also been found to cause kidney and liver damage, embryo loss during pregnancy and genetic damage. It often causes skin rashes, and people exposed to it can become very sensitive to it, requiring only a minute amount to cause a reaction. A major breakdown product of it (4-hydroxy-2,5,6-trichloroisophthalonitrile) is about 30 times more acutely toxic than chlorothalonil itself and is more persistent in soil.(Cox 1997)

It has adverse effects on various forms of wildlife and is persistent in the environment, being found in groundwater, fog, seawater and air.

Pesticides you might be consuming in celery
  • Acephate
  • Chlorothalonil
  • Diazinon
  • Difenoconazole-cis
  • Difenoconazole-trans
  • Dithiocarbamates
  • Indoxacarb
  • Methamidophos
  • Permethrin-cis
  • Permethrin-trans
  • Pirimicarb
  • Pirimiphos-methyl
  • Procymidone
  • Propazine
It has been found in groundwater in four states of the US, and in the air approximately a mile from chlorothalonil-treated fields. Chlorothalonils ability to contaminate water long distances from where it is used was startlingly demonstrated in a U.S.Dept. of Agriculture study of the Bering Sea. Chlorothalonil was found in every fog sample collected, and in several of the sea water samples collected. Chlorothalonil is very highly toxic to fish, and concentrations as low as 2 parts per billion can cause gill damage and anaemia. It is also toxic to shrimp, frogs, beneficial micro organisms, and earthworms. In plants it can cause a variety of effects, including reductions in yield. (Cox 1997)

The dithiocarbamates are a group of fungicides including mancozeb, metiram, zineb and ziram which have a metabolite called ethylene thiourea (ETU). This breakdown product is a known endocrine disruptor (disturbs hormones), anti-thyroid agent, carcinogen (cancer-causing), mutagen (gene-damaging) and teratogen (causing birth defects). (Birnbaum 2003, Hurley 1998, Colborn 1996, IARC 1991). ETU can be concentrated upon processing and heating. In other words, if you cook a vegetable which has been sprayed with mancozeb (the most common), you will be increasing the amount of the dangerous metabolite.

The Food Safety Authority judges that these residues in our food are of no concern and it assumes, for example, that a little bit of a carcinogen or mutagen wont hurt you. However, there is no scientific basis for this assumption. Studies have been unable to establish a threshold for carcinogens. One study, for example, involving 24,000 mice, taking five years to plan and conduct, and costing almost $US7 million, still could not resolve whether there are safe levels for carcinogens. (MacIntyre 1989)

Endocrine disruptors, brought to light by research only over the last decade, can mimic or disrupt the normal functions of hormones, and tamper with the delicately balanced signalling system in the body, which governs a range of functions and developmental processes. Though their effects in human beings are still being debated, the evidence is mounting. From wildlife and animal studies in laboratories, there is growing concern that endocrine disruptors can cause developmental, reproductive, behavioural, immunological and physiological changes. Particularly worrisome is the threat that endocrine disruptors pose on the unborn. When acting on a developing foetus at critical periods, they can cause lasting damage at minute doses, which were previously not thought to be harmful. (Schantz 2001, Colborn 1996, Watts 2000)

Not all bad news

All this bad news should hopefully persuade you to seek out organic celery when you can get it. If you cant get it, there is some good news, however. The residues detected in celery now compared to 14 years ago do seem to be much lower. In MAFs 1991 survey which analysed 60 samples of celery, 17 pesticides were found and 97.7% of samples had pesticide residues. The average level of chlorothalonil found then was an astounding 2.6015ppm, compared to 0.2286ppm in the latest results, that is, about a tenth as much. Dithiocarbamates were also much more liberally applied: the average residue then was 1.7233ppm compared to 0.0267ppm now, more than 60 times less. (MAF 1992)

There is, nevertheless, no room for complacency. New Zealand still does not restrict dithiocarbamate usage, whereas the US does. Here you can even buy mancozeb from the supermarket! Our regulatory authority has no apparent qualms that a number of cancer-causing pesticides are found in our food and assumes that a foetus being exposed to endocrine-disrupting substances from pesticide residues in our food is of no toxicological concern.

What we would like to see is that the Food Safety Authority agree that reducing pesticide residues in our food is a good idea and, along with the Environmental Risk Management Authority (ERMA), embark on a number of strategies to achieve this aim. Restricting and phasing out questionable pesticides would be a start. We would be very pleased if the Authority were to acknowledge that organic growing is not just good for exports, but is a very desirable and feasible option for New Zealand, good not only for the environment but for us too!


Birnbaum LS, Fenton SE 2003: Cancer and developmental exposure to endocrine disruptors, Environ Health Perspect 111:389-394.

Colborn T, Dumanoski D, Myers JP 1996: Our Stolen Future: Are we threatening our fertility, intelligence and survival? A detective story, Little, Brown & Co. See also

Cox C 1997: Fungicide factsheet: Chlorothalonil, J Pesticide Reform, 16(4):14-20.

Hurley PM, Hill RN, Whiting RJ 1998: Mode of Carcinogenic Action of Pesticides Inducing Thyroid Follicular Cell Tumors in Rodents, Environ Health Perspect 106:437-445

International Agency for Research on Cancer (IARC) 1991: Fungicides:. IARC Monogr Eval Carcinog Risks Hum 53:403-422.

MacIntyre A, Allison N, Penman D: Pesticides 1989: Issues and options for New Zealand, Ministry for the Environment

MAF 1992: Pesticide Residues in NZ Food 1990-1991. Department of Health & Ministry of Agriculture.

Schantz SL, Widholm JJ 2001: Cognitive effects of endocrine-disrupting chemicals in animals, Environ Health Perspect 109:1197-1206.

Vannoort RW: 2003/04 New Zealand Total Diet Survey Analytical Results - Q1 20 November 2003, Q3 8 July 2004, New Zealand Food Safety Authority & ESR.

Watts, M. 2000: Endocrine disruption: a case for the precautionary approach. Soil & Health March/April.

This article first appeared in OrganicNZ Nov/Dec 2004.

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