Malathion Profile

PESTICIDES  PROBABLE CARCINOGEN (IARC 2A)

CAS No. 121-75-5
IARC Monograph Vol. 30 Suppl. 7, 1983 (Group 3)
IARC Monograph Vol. 112, 2015 (Group 2A)

Malathion Profile

QUICK SUMMARY

  • A pesticide used in agricultural and commercial settings
  • Associated cancers: Non-Hodgkin lymphoma, prostate cancer (limited evidence)
  • Most important route of exposure: Inhalation, skin contact
  • Uses: Controls insects on field crops and blueberries, and in grain sheds, barns, and silos; emergency control for specific insects in fruit and berry crops
  • Occupational exposures: Farm workers, pesticide applicators, and mosquito control applicators most likely to be exposed
  • Environmental exposures: Via contaminated air near spray sites or touching objects with malathion residue
  • Fast fact: Malathion is occasionally used to control the spread of West Nile Virus in Winnipeg.

General Information

Malathion is an organophosphate insecticide. It’s appearance can range from a colourless to amber liquid, with a strong skunk or garlic-like odour. Malathion may also be known as its chemical name, which is O,O-dimethyl dithiophosphate of diethyl mercaptosuccinate.[1] As of late 2016, 26 products registered with the Canadian Pest Management Regulatory Agency (PMRA) contain the active ingredient malathion and of these, seven are registered for domestic use.[2] Trade names include Fyfanon® and Gardal Rose®.[2] Malathion was re-evaluated by the PMRA in 2012 and certain uses were subjected to a phase-out period. These uses include larval mosquito control and applications to greenhouse food and non-food crops, residential lawns, or livestock.[3]

Malathion is used as a broad-spectrum insecticide in the agricultural and domestic sector. It is also used to control fruit fly and adult mosquito populations, for example in campaigns to eradicate the West Nile Virus.[4]

The International Agency for Research on Cancer (IARC) reclassified malathion as Group 2A, probably carcinogenic to humans , in its 2015 assessment of five organophosphate pesticides.[5] IARC came to this conclusion due to limited evidence of carcinogenicity in humans for non-Hodgkin lymphoma and prostate cancer.[6,7,8,9,10] There was also sufficient evidence in animal and in vitro studies for carcinogenicity, DNA and chromosomal damage, and hormonal disruption.[11,12]

Malathion irreversibly binds to cholinesterase, the enzyme responsible for breaking down acetylcholine throughout the nervous system in humans, animals, and insects.[13] Malathion can be metabolized into malaoxon, which is substantially more toxic.[13] Human studies show that malathion reduces cholinesterase activity, and can also cause respiratory, gastrointestinal, and neurological symptoms.[4,14] In animals, malathion is a known endocrine disruptor, teratogen (disrupts embryo or fetus development), and reproductive toxin,[14,15,16,17] although these effects have not been confirmed in human studies.

Regulations and Guidelines

Occupational Exposure Limits (OEL)

Canadian Jurisdiction OEL (mg/m3)
Canadian Labour Code[18] 1(TWA; IFV; sk)
AB[19] 1 (TWA; sk)
BC[20] 1 (TWA; v; sk)
MB[21], NS[22], NL[23], PE[24] 1(TWA; IFV; sk)
ON[25] 1 (TWA; IFV; sk)
NB[26], QC[27] 10 (TWA; sk)
NT [28], SK[29], NU[30] 1 (TWA; IFV; sk)
3 (stel; IFV; sk)
YK[31] 10 (TWA; sk)
10 (stel; sk)
Other Jurisdictions OEL (mg/m3)
ACGIH’s 2018 TLV[32] 1 (TWA; IFV; sk)
mg/m3 = milligrams per cubic meter
TWA = time-weighted average, assuming a typical 8-hour workday and a 40-hour workweek of a chemical substance present in the air in a worker’s respiratory zone.
IFV = inhalable fraction and vapour
sk = easily absorbed through the skin; identifies substances that contribute significantly to overall exposure by the skin route
v = inhalable fraction, vapour and aerosol
stel = short term exposure limit (15 min. maximum)
ACGIH = American Conference of Governmental Industrial Hygienists
TLV = threshold limit value

Canadian Environmental Guidelines

Jurisdiction Limit Year
Ontario Ambient Air Quality Criteria AAQC = 120 µg/m3 2016[33]
British Columbia’s Contaminated Sites Regulation Soil standards:
Agricultural and low density residential sites: 300 µg/g
Urban park and high density residential sites: 650 µg/g
Commercial and industrial sites: 4500 µg/g
Drinking water standards: 190 µg/L
2017[34]
Quebec’s Regulation Respecting the Quality of Drinking Water MAC = 0.14 mg/L 2015[35]
Canadian Drinking Water Guidelines MAC = 0.19 mg/L 2017[36]
Health Canada’s Maximum Residue Limits for Foods Food type:
Cauliflower, eggplant, potatoes = 0.5 ppm
Wheat flour = 2 ppm
Asparagus, spinach, peaches = 6 ppm
Raspberries, strawberries = 8 ppm
Apricots, cereals = 8 ppm
Range = 0.5-8 ppm
2011[37]
Agreement Respecting the Great Lakes Basin Ecosystem Listed as a “Hazardous Polluting Substance” but no guidelines developed 1987[38]
CCME Water Quality Guideline Rank = “Medium hazard” 2008[39]
WHO’s Drinking Water Guideline Malathion: “Occurs in drinking-water at concentrations well below those of health concern” 2011[40]
µg/m3 = micrograms per cubic meter
mg/m3 = milligrams per cubic meter
mg/L = milligrams per litre
AAQC = Ambient Air Quality Criteria as measured over 24 hours
MAC = maximum allowable concentration
ppm = parts per million
CCME = Canadian Council of Ministers for the Environment
WHO = World Health Organization

Canadian Legal Status[41]

Jurisdiction Legislation Title Notes
Federal Pest Control Products Act, SC, 2002, c 28 Not included
  Pest Control Products Regulations, SOR/2006-124 Not included
Provincial/Territorial    
AB, BC, NB, NL, NT, NU, SK, YK Multiple titles Not included.
MB Non-Essential Pesticide Use Regulation, Man Reg 285/2014 Malathion is not allowed for domestic/cosmetic use.
NS List of Allowable Pesticides Regulations, NS Reg 181/2010 Malathion is not allowed for domestic/cosmetic use.
ON Pesticides Act, RSO 1990, c P. 11, as amended by the Cosmetic Pesticides Ban Act, 2008, S.O. 2008, c. 11, Bill 64 – Assented to: June 18, 2008 Malathion is not allowed for domestic/cosmetic use.
PE General Regulations, PEI Reg EC761/05 Malathion is not allowed for domestic/cosmetic use.
QC Pesticides Management Code, CQLR c P-9.3, r 1 Malathion is not allowed for domestic/cosmetic use

Several provincial, territorial, and municipal governments have passed laws to reduce risk to human health and the environment from pesticide products, which may include a restriction on sales, production, or trade.[42,43] Although several provinces and one territory have implemented some form of cosmetic pesticide policy (QC, 2003; NB, 2009; ON, 2009; AB, 2010; PEI, 2010; NS, 2011; NL, 2012; YK 1994), only the Ontario and Nova Scotia legislation is considered strong enough to significantly reduce cosmetic pesticide exposure.[42] For example, Ontario’s Cosmetic Pesticide Ban Act, the most comprehensive restrictions on lawn and garden pesticides in North America, prohibits the cosmetic use of over 250 pesticide products and over 95 pesticide ingredients, including malathion.[44]

Main Uses

Malathion was first registered for use in Canada in 1953.[3] It was re-evaluated by the PMRA in 2012, and certain uses were subjected to a phase-out period; these uses include larval mosquito control, and applications to greenhouse food and non-food crops, residential lawns, or livestock.[3] Malathion is a broad-spectrum insecticide used in agricultural, commercial, and domestic sectors. It can be formulated into sprays, fogs, pellets, powders, shampoos, and lotions.[3,45]

Examples of malathion use in Canada include:

 

  • Agriculture: to control pests in field crops such as alfalfa, clover pasture, cereal crops, cotton, safflower, soybean, sugar beets, corn, beans, and blueberries. It is registered for the emergency control of spotted wing drosophila in Canada for a variety of fruit and berry crops.[46,47] It is also used to control insects in storage areas such as grain sheds, barns, processing facilities, shipping crates, and silos.[48] Large-scale aerial applications of malathion are sometimes used.[14]
  • Domestic: the technical registrant of malathion in Canada voluntarily discontinued a number of residential uses including structural (pet quarters, indoor uses), companion animals, turf, and residential outdoors.[3] In the past malathion was used to control the spread of West Nile Virus in Canada, although currently this only appears to be practiced in Winnipeg, Manitoba.[49,50] These mosquito control programs use an ultra-low volume of malathion applied via fogging in residential areas, and residents may register for buffer zones around their homes.[49] Malathion was used to treat head lice and scabies in Canada and the United States,[4] although such treatments are no longer used or available in Canada.[51,52]
  • Commercial: to control indoor insects in food processing plants, schools, hospitals, golf courses, and dog kennels.[4]

Canadian Production and Trade

Since November 2006, the PMRA has tracked and reported sales information on Canadian pesticides. PMRA records show that more than 50,000 kilograms of active ingredient (kg a.i.) of malathion was sold in Canada in 2008, 2010, 2011, and 2012.[53,54,55,56] There was less than 50,000 kg a.i. of malathion sold in Canada in 2009.[57] Overall, malathion was not among the top 10 insecticides sold in Canada during the years reported. TradeMap lists malathion export and import data; however, reporting for pesticides is not standardized and the data is incomplete.[58]

Environmental Exposures Overview

The public may be exposed to malathion via inhalation or by touching objects with the chemical residue. People living near spray sites or in areas where this insecticide is used for West Nile Virus and mosquito control measures may be exposed.[13] Exposure to malathion may also take place by ingesting contaminated food or drinking water. Pesticide residues, including malathion residues, are monitored by the Canadian Food Inspection Agency (CFIA) under the National Chemical Residue Monitoring Program (NCRMP).[59]

Malathion may contaminate the environment at its site of production or use through accidental or intentional releases.[13] If malathion is released to air it may exist as a particulate or vapour. The vapour phase of this chemical is broken down into hydroxyl radicals with a half-life of five hours.[13] The particle phase may fall to the soil or water with rainfall or independently. The half-life of malathion in soil is 1-17 days, where it may volatilize back into the atmosphere, bind to soil particles, get taken up by plants, or be metabolized by soil microbes.[60] In water, it also binds to sediments, with a half-life of 10 days, or two days in the marine environment.[13] Malathion does not biomagnify or bioaccumulate.[13]

Occupational Exposures Overview

The primary routes of occupational exposure to malathion are inhalation and dermal absorption. Occupational exposure can occur during mixing, loading, or applying pesticides.[61] The people most likely to be occupationally exposed to malathion are farm workers, pesticide applicators, and mosquito control applicators.[13,62]

Sources

1. National Institute for Occupational Safety and Health (NIOSH). Pocket Guide to Chemical Hazards with the Centers for Disease Control and Prevention (Search term: malathion)
4. Gervais JA, Luukinen B, Buhl K, Stone D. National Pesticide Information Center (NPIC)’s Malathion Technical Fact Sheet (2009) (PDF)
5. International Agency for Research on Cancer (IARC). Monograph Volume 112: evaluation of five organophosphate insecticides and herbicides (2015) (PDF)
6. Waddell BL, Zahm SH, Baris D, Weisenburger DD, Holmes F, Burmeister LF, Cantor KP, Blair A. “Agricultural use of organophosphate pesticides and the risk of non-Hodgkin’s lymphoma among male farmers (United States)”. Cancer Causes and Control 2001;12:509-517.
7. McDuffie HH, Pahwa P, McLaughlin JR, Spinelli JJ, Fincham S, Dosman JA, Robson D, Skinnider LF, Choi NW. “Non-Hodgkin’s lymphoma and specific pesticides exposures in men: cross-Canada study of pesticides and health.” Cancer Epidemiol Biomarkers Prev 2001;10(11):1155-1163.
8. Eriksson M, Hardell L, Carlberg M, Akerman M. “Pesticide exposure as risk factor for non-Hodgkin lymphoma including histopathological subgroup analysis.” Int J Cancer 2008;123:1657-1663.
9. Band PR, Abanto Z, Bert J, Lang B, Fang R, Gallagher RP, Le ND. “Prostate cancer risk and exposure to pesticides in British Columbia farmers.” Prostate 2011;71:168-183.
10. Koutros S, Beane Freeman LE, Lubin JH, Heltshe SL, Andreotti G, Barry KH, DellaValle CT, Hoppin JA, Sandler DP, Lynch CF, Blair A, Alavanja MC. “Risk of total and aggressive prostate cancer and pesticide use in the Agricultural Health Study.” Am J of Epidemiol 2013;177:59-74.
11. Cabello G, Valenzuela M, Vilaxa A, Durán V, Rudolph I, Hrepic N, Calaf G. “A rat mammary tumor model induced by the organophosphorous pesticides parathion and malathion, possibly through acetylcholinesterase inhibition.” Environ Health Perspect 2001;109:471-479.
13. US National Library of Medicine. Hazardous Substance Database (HSDB) (Search term: malathion)
14. Agency for Toxic Substances and Disease Registry (ATSDR). Public Health Statement: Malathion (2003)
15. Pournourmohammadi S, Farzami B, Ostad SN, Azizi E, Abdollahi M. “Effects of malathion subchronic exposure on rat skeletal muscle glucose metabolism.” Environ Toxicol Pharmacol 2005;19:191-196.
16. da Silva AP, Meotti FC, Santos AR, Farina M. “Lactational exposure to malathion inhibits brain acetylcholinesterase in mice.”Neurotoxicology 2006;27:1101-1105.
19. Government of Alberta. Occupational Health and Safety Act 568 (2009) (PDF)
23. Government of Newfoundland and Labrador. Occupational Health and Safety Regulations 5/12 (2012)
24. Government of Prince Edward Island. Occupational Health and Safety Act Regulations Chapter 0-1, 119 (2013) (PDF)
28. Government of the Northwest Territories. Occupational Health and Safety Regulations, R-039-2015 (2016) (PDF)
29. Government of Saskatchewan. The Occupational Health and Safety Regulations, 1996 (2016) (PDF)
31. The Canadian Legal Information Institute (CanLII). Yukon’s Occupational Health Regulations, O.I.C. 1986/164 (2012) (PDF)
32. Occupational Safety and Health Administration (OSHA). Annotated PELs (2018)
33. Ontario Ministry of the Environment and Climate Change. Ontario’s Ambient Air Quality Criteria (2016)
34. Government of British Columbia. Contaminated Sites Regulation B.C. Reg. 375/96 (2017)
35. The Canadian Legal Information Institute (CanLII). Regulation respecting the quality of drinking water, CQLR c Q-2, r 40 (2015)
38. International Joint Commission. Revised Great Lakes Water Quality Agreement of 1978 (1987) (PDF)
39. Canadian Council of Ministers of the Environment (CCME). National Classification System for Contaminated Sites: Guidance Document (2008) (PDF)
41. The Canadian Legal Information Institute (CanLII). The Canadian Legal Information Institute (CanLII) (2015)
44. Government of Ontario. Pesticides Act (2015)
45. National Pesticide Information Centre (NPIC). Malathion General Fact Sheet (2010) (PDF)
46. Ontario Ministry of Agriculture Food and Rural Affairs. Pesticide Registrations: Spotted Wing Drosophila in Ontario (2015)
47. Perennia Extension and Advisory Team. Emergency Registration for Spotted Wing Drosophila (2015) (PDF)
48. Beyond Pesticides. Malathion chemicalWATCH Factsheet (2000) (PDF)
51. Health Canada. Drug Product Database (2015)
52. Cummings C, Finlay J, Macdonald N. “Head lice infestations: A clinical update.” Paediatr 2014;13:692-696.
58. International Trade Centre. Trade Map (Free subscription required)
59. Canadian Food Inspection Agency. Chemical Residues in Food (2016)
60. Getenga ZM, Jondiko JIO, Wandiga SO, Beck E. “The dissipation of malathion and dimethoate from the pea plants (Pisum sativum) under controlled conditions.” Toxicol Environ Chem 2000;77:219-228.
61. US Environmental Protection Agency (EPA). Occupational Pesticide Handler Exposure Data (2013)
62. Kongtip P, Sasrisuk S, Preklang S, Yoosook W, Sujirarat D. “Assessment of occupational exposure to malathion and bifenthrin in mosquito control sprayers through dermal contact.” J Med Assoc Thai 2013;96:S82 -91.

 

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