herbicide atrazine is used throughout the world for a varied range of
uses. It is an environmental contaminant regularly found in rain, surface,
marine, and ground water. Recent research has suggested a link between
atrazine exposure and serious effects on the sexual development of frogs.
Atrazine is a selective systemic herbicide(1) introduced in 1958(2)
by J.R. Geigy (now part of Novartis)(3). Novartis is atrazine’s
largest manufacturer(4); it is one of their best selling products(5)
but it is also manufactured by a number of other companies and has a
range of trade names including Marksman (Novartis), Coyote (Defensa),
Atrazina (Cequisa), Atrazol (Sipcam) and Vectal (Aventis)(6). Atrazine
is used for the pre and post-emergence control of annual and broad leaved
weeds and perennial grasses(7); it inhibits photosynthesis and interferes
with other enzymic processes(8). It is mainly absorbed through the plant
roots, but can enter through the foliage, and accumulates in the apical
meristems and leaves(9).
atrazine is used in the production of maize, sorghum, sugar cane, pineapples,
chemical fallows, grassland, macadamia nuts, conifers, and for industrial
weed control(10), with its biggest market in maize production(11). In
Europe, its use is concentrated on maize, orchards and vineyards(12),
and in the UK, it is mainly used for maize, forestry, roses, and grassland(13).
Atrazine is also applied in combination with many other herbicides(14),
for example with simazine, another triazine chemical(15).
is applied worldwide – in 1998 it was the most widely used maize
herbicide in the US, applied to 69% of the maize acreage(16). The world
market for atrazine is worth over $400 million at the user level(17).
In Europe atrazine consumption has dropped markedly since 1989(18) due
to restrictions on its use and competition from newer, less-persistent
herbicides(19). In the UK, atrazine is not widely applied, however it
does have significant uses in maize production for general weed control,
for which there are no alternatives(20). For example, in 1997 atrazine
was applied to 53% of the herbicide treated area of maize in the UK(21).
Its use is on the increase, reflecting the expansion of maize cultivation:
applications of atrazine to UK grassland and fodder crops rose from
24,120 spray hectares in 1989 to 109,602 in 1997(22). Atrazine is also
an important pesticide for rose cultivation and the forestry industry
– in 1997, from a total of 25,092 spray hectares on hardy nursery
stock, atrazine accounted for 884 spray hectares(23).
application of atrazine is for total weed control on non-crop land such
as railways, roadsides and industrial areas(24). In the past, it was
widely used for this purpose, however in recent years this use has been
restricted in some countries. In the UK for example, approval for use
of atrazine on non-cropped land was revoked in 1992 (with the exception
of the home/garden situation) following concerns over residue levels
in drinking water(25) (see below).
is classified by the WHO as a pesticide unlikely to present acute hazard
in normal use(26). The acute oral LD50 (dose at which half the sample
is dead) for rats is 1869-3090 mg/kg(27) and for mice it ranges from
>1332-3992 mg/kg(28). These LD50 levels indicate atrazine’s
low toxicity – the Advisory Committee on Pesticides (ACP) evaluation
stated atrazine is of low oral, inhalational and percutaneous acute
toxicity(29). Interestingly, ruminants seem to be much more sensitive
to the acute toxic action than rodents, in one study, two doses of 250mg/kg
caused death in both sheep and cattle(30). Atrazine is a mild skin irritant(31)
and is moderately irritating to the eye(32); for example, Atrazine 90DF
causes ‘substantial but temporary eye irritation’(33).
highest likelihood of human exposure to atrazine is associated with
its production and use in agriculture. The results of one study in the
US showed that applicators of atrazine are experiencing detectable exposures
during one-time application through dermal absorption, inhalation or
both(34). Additionally, the public at large may be subject to exposure
through the consumption of contaminated drinking water(35).
(birth defects)The International Programme on Chemical Safety (IPCS)
concludes that ‘atrazine has no significant teratogenic action
in rats, mice or rabbits’(36) and the ACP does not consider atrazine
to be teratogenic(37).
in-depth review of the toxicology of atrazine states ‘studies
of exposed people and laboratory tests show that atrazine and atrazine-containing
herbicides reduce the ability to reproduce successfully’(38).
The review examines a number of studies to validate this, for example
one study found the incidence of premature birth in families in which
the father applied atrazine on the farm was nearly double that of families
in which the father was not exposed to pesticides(39).
ACP and the US Environmental Protection Agency (EPA) evaluations both
concluded atrazine does not have a mutagenic effect(40). However, the
Northwest Coalition for Alternatives to Pesticides (NCAP) believe that
the EPA review omitted studies that raise serious concerns about atrazine’s
mutagenicity, for example, one study found a significant increase in
the percentage of chromosomal damage in the blood cells of workers in
an atrazine production plant(41).
carcinogenicity of atrazine is a controversial subject that has been
studied in both people and laboratory animals(42). From experiments
on rats, the ACP concluded atrazine increased the occurrence of mammary
gland carcinomas in the rat strain studied, but not in other species(43);
from evaluating the available evidence the IPCS found there was no convincing
evidence of carcinogenicity in rats or mice(44). In contrast, in human
evaluations, one study on the incidence of breast cancer and ovarian
cancers in Kentucky found the breast cancer risk was higher (1.1-1.2
fold) in counties with medium and high levels of triazine exposure than
it was in counties with low exposure(45). However, a later study carried
out with a similar design, did not find any association between atrazine
and breast cancer, and indeed an inverse association with ovarian cancer(46).
In 2001, the NCAP evaluated all the available studies on cancer. They
came to the conclusion that the results of an IACR evaluation stating
‘atrazine is not classifiable as to its carcinogenicity to humans’
(due to inadequate evidence(47)) were appropriate(48).
is only slightly toxic to birds(49) – there is no mortality at
10,000 mg/kg diet(50). It is virtually non-toxic for bees(51) with an
LD50 (contact) of >1000µg/bee. Atrazine is classified as moderately
toxic for aquatic organisms (96-h LC50 range from 0.5-15mg/litre(52))
by the IPCS, the LD50 for catfish is 7.6 mg/l and 4.3 mg/l for guppies(53).
It has been said that atrazine is degradable and has little tendency
to bioaccumulate(54), thereby limiting possible long-term adverse effects
on fish and wildlife(55).
recent research in the US has shown atrazine has serious effects on
frogs’ sexual development. The research has found that atrazine
at levels often found in the environment demasculinises tadpoles and
turns them into hermaphrodites, with males having ovaries in their testes
and much smaller vocal organs, and with ten times lower levels of testosterone
than normal male frogs(56). The herbicide apparently modifies the steroid
hormone balance in frogs at a sensitive time in their development(57).
Researchers are now testing native leopard frogs from the American Mid-West
with similar problems to determine whether the changes are due to atrazine(58).
This research raises concern for all aquatic life that swims and breeds
in atrazine-contaminated field runoff.
it is an effective herbicide, in addition to direct toxic effects, the
phytotoxicity of atrazine may constitute a problem in the case of uncontrolled
applications(59) and indirectly affect aquatic animal populations by
changes in water quality caused by their removal, for example decreased
dissolved oxygen levels and reduced plant cover(60).
in the environment
is a pervasive environmental contaminant(61). It is strongly persistent
and is one of the most significant water pollutants in rain, surface,
marine, and ground water(62). Its persistence (it has a half-life of
125 days in sandy soils(63)) and mobility in some types of soils because
it is not easily absorbed by soil particles(64), means it often causes
contamination of surface and ground waters(65). In the US for example,
it has been found in the groundwater of all 36 river basins studied
by the US Geological Survey(66) (USGS) and the USGS estimates that persistence
in deep lakes may exceed 10 years.
weeds have developed resistance to atrazine. For example, atrazine resistant
strains of the weeds Chenopodium and Amaranthus were collected from
maize fields in the US that had been treated with atrazine for 12 years(67).
In the UK rose industry, groundsel (Senecio vulgaris) has been identified
as triazine resistant(68). As a result of this tendency for the development
of resistance, there are restrictions on the number of applications
that can be made to crops(69).
light of the widespread groundwater contamination highlighted above,
concerns have arisen over atrazine residues in drinking water. These
concerns have now led to bans in Austria, Slovenia, Germany, Denmark
and Italy, and atrazine is subject to restrictions in several other
European countries including France and the UK(70). However, in the
UK, throughout the evaluation process, the ACP and the Ministry of Agriculture
made a point of stressing that restrictions imposed on atrazine are
not the result of any health risk, but only to keep residue levels in
water within the legally imposed EC Drinking Water Directive limit of
0.1 µg/l for any single pesticide(71), a level which was not a
level derived from toxicological studies.
the US, the US EPA has established a Lifetime Health Advisory level
for atrazine in drinking water of 3 µg/l, i.e. water containing
atrazine at or below this level is acceptable for drinking every day
over the course of one’s lifetime, and does not pose any health
advocates of atrazine may feel the problem has been exaggerated. A Ciba-funded
study in the US in 1996 showed that in 99.7% of drinking water supplies
tested, atrazine residues were either not present or did not exceed
the EPA’s standard. In those areas where the level exceeded the
standard, Novartis is said to be co-operating with the local communities
to reduce exposures(73). In fact, the company argues that ‘any
ban on atrazine, based on political and other considerations rather
than scientific argument, could set a dangerous precedent for the crop
protection industry in its dealings with government authorities’.(74
Europe atrazine is now pending review for inclusion on Annex 1 of the
91/414 directive on pesticides. The outcome of this process is likely
to be controversial as if atrazine is included on Annex 1, some countries
would have to re-permit atrazine use, but, for example, Germany has
already indicated that it is reluctant to change its stance(75). By
March 2000, atrazine had completed the peer review stage and entered
one of the final stages of the EU review process. Two years later, the
final Annex 1 decision is still awaited(76).
is a pesticide of major concern for a number of reasons including possible
negative health effects, effects on aquatic organisms, levels in drinking
water and the development of resistance. Whilst it is becoming less
widely used, the effects of its long-term persistence may still cause
health and environmental problems in the future. (HM)
1. Advisory Committee on Pesticides, Evaluation on Atrazine (2), Evaluation
of Fully Approved or Provisionally Approved Products, No. 71, Ministry
of Agriculture, Food and Fisheries, London, July, 1993.
2. IPSC International Programme on Chemical Safety, Atrazine Health
and Safety Guide No. 47, WHO Geneva, 1990.
3. Hicks B, Generic Pesticides – The Products and Markets, Agrow
Reports, PJB Publications, 1998.
4. Hicks, Ibid.
5. Dewar A, Agrow’s Top 25 – 2001 Edition, Agrow Reports,
PJB Publications, April 1998.
6. Tomlin CDS (Ed), Pesticides Manual 12th Edition, British Crop Protection
7. Tomlin, Op. cit. 6.
8. MAFF, Op. cit. 1.
9. MAFF, Ibid.
10. Tomlin, Op. cit. 6.
11. Hicks, Op. cit. 3
12. MAFF, Op. cit. 1.
13. MAFF, Ibid.
14. Tomlin, Op. cit. 6.
15. Pesticides Usage Survey Report, Hardy Nursery Stock, Number 152,
Ministry of Agriculture, Fisheries and Food and Scottish Office Agriculture,
Environment and Fisheries Department, 1997.
16. Dewar, Op. cit. 4.
17. Hicks, Op. cit. 3.
18. Hicks, Ibid.
19. Dewar, Op. cit. 4.
20. Davis M, Atrazine and Simazine: Restrictions now effective, Pesticides
News, September 1993, Vol. 21, page 19, September 1993.
21. Pesticides Usage Survey Report, Grassland and Fodder Crops, Number
151, Ministry of Agriculture, Fisheries and Food and Scottish Office
Agriculture, Environment and Fisheries Department, 1997.
22. Pesticides Usage Survey Report, ibid.
23. Pesticides Usage Survey Report, Op. cit. 15.
24. MAFF, Op. cit 1.
25. Advisory Committee on Pesticides Annual Report, Ministry of Agriculture,
Food and Fisheries, 1992.
26. IPCS, The WHO recommended classification of pesticides by hazard
and guidelines to classification 1998-1999, WHO/IPCS/98.21.
27. Tomlin, Op. cit. 6
28. Tomlin, Ibid.
29. MAFF, Op. cit. 1.
30. IPCS, Op. cit. 2.
31. MAFF, Op. cit. 25
32. IPCS, Op. cit. 2.
33. Cox C, Herbicide Factsheet, Atrazine: Toxicology, Journal of Pesticide
Reform, 2001, Vol 21, No. 2.
34. Perry M, et. al., Urinalysis of atrazine exposure in farm pesticide
applicators, Toxicology and Industrial Health, 2000, vol. 16, 285-290.
35. IPCS, Op. cit. 2.
36. IPCS, Ibid.
37. MAFF, Op. cit. 25.
38. Cox, Op. cit. 33.
39. Savitz et. al., cited by Cox, Op. cit. 33.
40. MAFF, Op. cit. 1; Cox, Op. cit. 33.
41. Cox, Op. cit. 33.
42. Cox, Ibid.
43. MAFF, Op. cit. 1.
44. IPCS, Op. cit. 2.
45. Kettles et. al., cited by Cox, Op. cit. 33.
46. Hopenhayn-Rich C, Stump ML and Browning SR, Regional Assessment
of Atrazine Exposure and Incidence of Breast Cancer and Ovarian Cancers
in Kentucky, Archives of Environmental Contamination and Toxicology,
2002, 42, 127-136.
47. International Agency for Research on Cancer, cited by Hopenhayn-Rich
et. al., ibid.
48. Cox, Op. cit. 33.
49. Pesticide Management Information Programme ‘Atrazine’
EXTOXNET Pesticide Information Notebook, Cornell University, New York,
50. IPCS, Op. cit. 2.
51. IPCS, Ibid.
52. IPCS, Ibid.
53. Tomlin, Op. cit. 6.
54. IPCS, Op. cit. 2
55. IPCS, Ibid.
56. Sanders R, University of California, Berkeley, Campus News, Media
Relations, Press Release, Popular weed killer demasculinizes frogs,
disrupts their sexual development, UC Berkeley study shows, www.berkeley.edu/news/media/releases/2002/04/15_frogs.html,
57. Atrazine linked to endocrine disruption in frogs, Environmental
Science and Technology, February 1, 2002.
58. Saunders, Op. cit. 56.
59. IPCS, Op. cit. 2.60. MAFF, Op. cit. 1.
61. Cox C, Herbicide Factsheet, Atrazine: Environmental Contamination
and Ecological Effects, Journal of Pesticide Reform, Fall 2001, Vol
21, No. 3.
62. Wiegand C, et. al., Toxicokinetics of Atrazine in Embryos of the
Zebrafish (Danio rerio), Ecotoxicol. and Environmental Safety, 2001,
63. IPCS, Op. cit. 2.
64. ECOTOXNET, Op. cit. 49.
65. IPCS, Op. cit. 2.
66. US Geological Survey, cited by Cox, Op. cit 61.
67. Solymosi et, al,, cited by Cox, Op. cit. 61.
68. Pesticide Usage Survey Group, Op. cit. 21.
69. Whitehead R (Ed.), The UK Pesticide Guide 2002, British Crop Protection
Council and CABI Publishing, 2002.
70. Hicks, Op. cit. 3
71. Davis, Op. cit. 20.
72. ECOTOXNET, Op. cit. 49.
73. Hicks, Op. cit. 3
74. Hicks, Ibid.
75. Hicks, Ibid.
76. Dewar, Op. cit. 5.
[This article first appeared in Pesticides News No. 56, June 2002, pages