Pesticide Residues in Coastal Tropical Ecosystems: Distribution, fate and effects - Chapter 7 potx

The economic benefits of pesticide use in producing high crop yieldsand the role of pesticides in the control of disease-borne pests are undeniable.Equally the adverse effects of elevate

Malaysia is currently one of the world’s primary exporters of natural rubberand the world’s primary exporter of palm oil These together with cocoa, pepper,pineapple, and tobacco comprise the main crops responsible for the growth of thissector Agriculture has also been an important base for the development of othersectors of the Malaysian economy, particularly the manufacturing sector asexemplified by the food and beverage industry.

The pesticide industry is one of the most important support industries inagriculture The economic benefits of pesticide use in producing high crop yieldsand the role of pesticides in the control of disease-borne pests are undeniable.Equally the adverse effects of elevated pesticide residues in water, soil, and crops

to man, domestic animals, wildlife, and the environment are well recognized anddocumented

In tropical countries like Malaysia, crops such as rice and vegetables areparticularly susceptible to the negative impacts of pesticide use (ADB, 1987) This

is attributed to the often indiscriminate and intensive use of pesticides associatedwith these crops The problem is exaggerated by the inadvertent destruction ofthe pest’s natural enemies, and the emergence of resistant pest strains, the conse-quence of which is the application of increasingly larger amounts of pesticides.Other crops, including palm oil and rubber, also require intensive use of pesticides,particularly herbicides

In addition to their use in agriculture, pesticides have also contributed to thecontrol of insect-borne diseases Pest control programs to improve public health

in Malaysia have been primarily directed toward the eradication of mosquitoes.Under the Malaria Eradication Program initiated in 1967, wall surfaces insidehomes of malaria-infected areas were sprayed with DDT Dengue fever wassimilarly brought under control by large-scale spraying programs using insecticidessuch as pyrethrins, malathion, and temephos (Abate) Other diseases such as typhus(carried by body lice) and dysentery (carried by flies), once rampant and greatlyfeared, have been either curtailed or practically eradicated by the application ofpesticides in addition to other public-health related strategies Recently, researchhas focused on evaluating the efficacy of alternatives to DDT and other OCs –

specifically OPs, pyrazoles, and pyrethroids – or controlling disease vectors (Yap et

al., 1996; Sulaiman et al., 1999; 2000).

The objective of this chapter is to examine various aspects of pesticide use inMalaysia, including current trends, levels of contamination in the aquatic environ-ment, as well as impacts of pesticide use In addition, recommendations andsuggestions are put forward with respect to both mitigation measures, and essentialareas of additional research

A G R I C U LT U R E A N D P E S T I C I D E S

In a relatively short period of time, Malaysia became a major producer of primarycommodities and assumed a dominant world position in rubber, palm oil, andcocoa The location of the major agricultural areas on Peninsular Malaysia isgiven in Figure 7.1

Currently oil palm remains the favored crop, while rubber and cocoa haveundergone a decline in acreage in recent years (see Figure 7.2) (MACA 1997) In

1996, the number of hectares devoted to oil palm increased by 2.4 percent fromthe previous year to 2.6 M ha Indeed, Malaysia is currently the world’s leadingproducer of palm oil at 53 percent of total world palm oil production in 1993(MADI, 1996)

The decrease in acreage for rubber and cocoa has been attributed to the shortage

of labor as well as the conversion of land to other crops, particularly oil palm, andfor commercial and residential uses The area under rice paddy culture has alsobeen on the decline (Figure 7.2) In order to achieve a targeted 65 percent self-sufficiency in rice, there has been an emphasis on increased crop intensity,mechanization, and varietal yield (HYV) improvements It should also be notedthat IPM has been widely promoted for rice paddies and has resulted in a reduction

of incidences of pest population explosions as was frequently reported in the 1970sand early 1980s These incidences particularly related to severe outbreaks of the

brown planthopper Nilaparvata lugens Stål (Homóptera: Delphacidae) and the backed planthopper Sogatella furcifera Horváth (Homóptera: Delphacidae) (MACA,

white-1997)

Although the importance of agriculture is declining, it continues to play animportant role in the development strategy of Malaysia Agriculture’s continued

importance lies in its contribution to the rural economy and to its link with othersectors of the economy by providing the raw materials for manufacturing andagronomic-based industries.

A National Agricultural Policy (NAP, 1984) was promulgated in 1984 to serve

as a guideline for Malaysia’s agricultural development up to the year 2000 A fewyears later, the policy was redefined as the NAP, 1992 to 2010 to emphasize variousstrategies such as the optimization of resource use, the development of relatedagro-based industries, and the enhancement of research and development activities.The success of the agriculture sector in Malaysia was achieved by the introduc-tion of sound and effective agricultural policies, coupled with the application ofmodern technologies NAP (1984) was aimed toward greater agricultural produc-tivity, emphasizing higher-value crops such as oil palm, cocoa, vegetables, fruits,and flowers Modern practices of large-scale continuous cropping of individual

Figure 7.1 The location of major agricultural areas by crop in Peninsular Malaysia

crops and the use of high-yielding strains were also encouraged Many of thebenefits obtained from the adoption of monoculture technology and the use ofHYV(s) are dependent on effective plant protection strategies Monocultures tend

to encourage rampant population growth of pest species by providing idealconditions for their development and reproduction Crop losses have also resulteddue to disease and pests encouraged by large-scale planting and genetic uniformity

of the crop, a consequence of using a limited range of HYV(s) Large-scalecontinuous cropping of individual crops also tends to encourage the growth ofpest species by providing the necessary conditions for their development Hence,improved management practices, including more cost-effective pest controlstrategies, have been introduced

The majority of the pesticides used in Malaysia are applied in the rubber, oilpalm, and rice sectors of agriculture As can be seen in Table 7.1, herbicides accountfor 75 percent of the total pesticide market, followed by insecticides (16 percent),fungicides (5 percent), and rodenticides (4 percent) (MACA, 1997) Table 7.2 lists

Figure 7.2 Change in the area planted in oil palm, rubber, cocoa, and rice in Malyasia for

the years 1980, 1990, and 1995 (MACA, 1997)

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Cocoa Rice Oil palm 0000000000Rubber

Table 7.1 Estimate of the pesticide market a in Malaysia (US$ M) b

a End-user value at a constant exchange rate of US$1 = RM2.5.

b Adapted from MACA, 1996; 1997.

some examples of commonly applied pesticides in oil palm, rubber, cocoa, andrice Herbicides used in Malaysia are predominantly in the form of aqueousconcentrates while the majority of insecticides and fungicides used are in the forms

of emulsifiable concentrates and wettable powders respectively (Abdullah, 1993).The use of herbicides has been and will continue to be an important aspect ofthe crop protection strategy in Malaysia as long as a labor shortage makes manual

Table 7.2 Commonly used pesticides in oil palm, rubber, cocoa, and rice in Malaysia a

Oil palm 2,4-D dimethylamine Carbofuran Captan

methylarsonate) + Endosulfan Thiram diuron + dicamba Methamidophos

Fluazifop-butyl Monocrotophos Glufosinate ammonium

Glyphosate Metsulfuron methyl Paraquat

Quinclorac, (a quinolinecarboxylic acid herbicide) Rubber Same as for oil palm Chlorpyrifos Hexaconazole,

Cypermethrin (a conazole

Tridemorph Chlorothalonil Cocoa Fluroxypyr methyl α-cypermethrin Captafol

heptyl ester, (a Cypermethrin + Copper pyridyloxyacetic acid chlorpyrifos oxychloride

Glufosinate ammonium Lindane Triadimenol

Oxyfluorfen Sodium chlorate

2,4-D butyl ester BPMC [2-(1-methyl- Thiram Bentazone propyl)phenyl Flutolanil, (a Metsulfuron methyl methylcarbamate] benzanilide

Endosulfan Lindane Diazinon

Note:

a Derived from MADI, 1996.

weeding uneconomical Most herbicide is applied on rubber and palm oil tions While older herbicides, e.g paraquat, glyphosate, glufosinate-ammonium,and 2,4-D, represent the bulk of herbicides used in Malaysia, there has also been

planta-an increase in popularity for the use of newer chemicals, e.g metsulfuron methyl,which require only low concentrations to be effective (MADI, 1996) It is alsonoteworthy that Malaysia exports a considerable quantity of pesticides, particularlyherbicides In 1993, herbicides worth US$10.8 million, e.g paraquat, 2,4-D amine,sodium chlorate, glyphosate, diuron, monuron, and linuron, were exportedprimarily to other countries in the region (MADI, 1997)

The use of insecticides, predominantly in vegetable production, is characterized

by the wide variety of available chemicals As with herbicides, newer, morebiologically active and environmentally friendly chemicals are increasingly popular.These chemicals tend to be more costly but are effective at lower concentrations.Fungicides are for the most part imported because their consumption is low, beingused mainly in vegetable, fruit, and flower production

The most common method of applying pesticides in Malaysia is spraying thepesticide solution onto crops with a knapsack sprayer This application techniquehas been proven to be inefficient as only about 20 percent of the spray reaches theplants, and less than 1 percent of the chemical contributes to pest control, resulting

in wastage and contamination of the environment (MADI 1996) This is attributable

to the variable size of the droplets, which tend to coalesce and run off the leafsurface, produced by such sprayers The fine mist generated by these sprayers alsotends to evaporate before reaching the plants Controlled droplet application (CDA)technology has been introduced to increase the efficacy of pesticides by restrictingthe droplet size to an optimum range In Malaysia the use of CDA has not beenwidespread due mainly to the higher cost of the sprayer but also to higher opera-tional and maintenance costs However, the use of CDA has become quite common

on the larger oil palm plantations (MADI, 1996)

In recent years there has been a gradual decrease in the growth of the pesticidemarket in Malaysia from an annual increase of 9 percent in 1992 to 3 percent in

1996 (estimated at end-user level) (MADI, 1997) The decreasing trend in pesticideuse has been attributed to the introduction of improved products with greaterefficacy and selectivity, more judicious application of the pesticides, and thedevelopment of biological control and integrated pest management strategies Someexamples of recently introduced pesticides include cyhalofop butyl (an aryloxy-phenoxypropionic herbicide), tralomethrin (a pyrethroid ester insecticide), andacetamiprid (a pyridine insecticide) These chemicals exhibit substantial reduction

in dosage rates and therefore smaller amounts are applied to treat the same area

of cultivated land Improved pest management practices have also contributed tothis trend, including such specialized biocontrol techniques as arthropod-dependent

(ant) protection from pests in cashew nut Anacardium occidentale (Anacardiaceae)

production (Rickson and Rickson, 1998) and parasitoid control of the diamondback

moth Plutella xylotella L (Lepidoptera: Plutellidae) in vegetable production (Verkerk

and Wright, 1997) New pesticide chemistry, biocontrol techniques, and IPM

procedures all contribute to the management of developed/developing resistance

in pest species because of improperly or excessively used pesticides Pesticideresistance studies in Malaysia have most often implicated phase I microsomalmonoxygenases and (or) esterases in the development of resistance to such diversepesticides as the carbamates propoxur and bendiocarb, the OP chlorpyrifos, thepyrethroids cypermethrin and permethrin, the antibiotic pesticide abamectin, the

chitin synthesis inhibitor teflubenzuron, and the biological insecticide Bt (Lee et

al., 1996; Iqbal and Wright, 1997; Verkerk and Wright 1997) However, Iqbal and

Wright (1997) did find some evidence for the involvement of phase II

glutathione-S-transferases in decreasing the toxicity of abamectin to P xylostella Resistance

management strategies must account for the development of cross-resistance, theuse and timing of synergists, and the management of parasitoids and other bio-control species

The pesticide industry in Malaysia is made up of about 140 companies – bothmultinational and local companies – that are involved in manufacturing, formu-lating, or trading activities (MACA, 1997) The majority of pesticides are imported

as technical materials, which are then blended, diluted, or formulated However,

in recent years an increasing variety of pesticides are being manufactured inMalaysia These include herbicides such as paraquat, sodium chlorate, dalapon,and glyphosate At present, the quantity of wastes generated by these industries israther small and generally manageable Current waste treatment systems includethose based on chemical degradation (alkaline hydrolysis, particularly for OPs)and those using oxidation ponds (Samad, 1991)

In addition to chemical pesticides, biological pesticides – best exemplified by

the bacterium Bacillus thuringiensis (Berliner) (BT) – have been introduced into the

Malaysian pesticide market BT’s specificity and versatility, in that different variantscan be developed for different pest species, are an important contribution in thepromotion of environmentally friendly and sustainable agricultural production.The pesticide industry is expected to continue to be an important component

of the agriculture sector in Malaysia Pesticides will continue to provide a reliableand cost-effective solution to pest and diseases problems As the number of hectares

of arable land is not expected to increase in the future – indeed, land conversions

to other non-agricultural uses have been taking place – the focus in agriculture hasbeen on increasing crop intensity and on yield improvements Hence, to meet theincreasing demands of a growing population, pesticides will continue to make animportant contribution to increasing yields and to the reduction of post-harvestlosses

P E S T I C I D E R E G U L AT O R Y P O L I C I E S

For many years, pesticide use in Malaysia was controlled by the Ministry of Healthunder the Poisons Ordinance, 1952 and the Poison List Order, 1970 under whichcertain highly toxic chemicals are banned from import or manufacture A Voluntary

Registration Scheme for pesticides was introduced in the 1960s and 1970s but wasdeemed to be unsatisfactory due to poor and inadequate response by the pesticideindustry This led to the introduction of specific legislative acts governing pesticideuse in Malaysia.

At present, the use of pesticides in Malaysia is governed by the Pesticides Act

of 1974, which regulates the importation, manufacture, distribution, sale, and use

of pesticides in Malaysia The Act came into force on 1 October 1976 and isadministered by the Pesticide Board of the Department of Agriculture The Actrequires that all pesticides be registered Registration is implemented under thePesticide (Registration) Regulations, 1976 (Pesticides Board Malaysia, 1991) Datarequirements are essentially in accordance with FAO guidelines The informationrequired to be submitted with the application for registration of new pesticidesincludes the physicochemical properties of the chemical, its efficacy, storage stability,toxicological data, residue data, known environmental impacts, and a declarationthat the pesticide has been approved for use in other countries that practice anacceptable registration procedure A proposal for a label for the pesticide is alsorequired based largely on FAO Guidelines on Good Labeling Practices for Pesticides(FAO, 1995)

The registration is valid for five years after which each registered pesticide isreassessed for its continued use In this way, several pesticides have either beenderegistered, e.g aldrin and dieldrin, or their use restricted following reassessment,e.g HCH and endosulfan This procedure takes into consideration safer alternativesand reported abuses among other factors

The use of pesticides deemed to be highly toxic is further governed by thePesticide (Highly Toxic Pesticides) Regulations of 1996 – particularly with respect

to specific handling restrictions – ensuring that workers handling these chemicals

do so with the utmost care Employers are required to provide adequate training

to workers, who must also be medically fit Workers are only permitted to work amaximum eight hours per day Employers are further required to maintain strictrecords detailing the number of hours worked, the type and amount of pesticideused, and the method of application Their workers are required to wear properprotective clothing and complete an annual medical examination Furthermore,these regulations dictate that, in the case of female workers, only those who arenot pregnant or lactating are permitted to handle pesticides Other requirementsinclude safe and proper storage of the chemicals and safe disposal of emptycontainers (Pesticides Board Malaysia, 1996) Handling pesticides such as paraquat,monocrotophos, and calcium cyanide is subject to these regulations The handling

of other pesticides not included in this particular list is not subject to the rigorousset of conditions stipulated in the Pesticide (Highly Toxic Pesticides) Regulations,

1996 but is, of course, required to comply with the Pesticide Act, 1974

Pesticide residues in food are controlled by The Food Regulations Act of 1985,which is enforced by the Ministry of Health MRL(s) for pesticide residues arestipulated in this Act The Act also provides for punitive action against those whomisuse pesticides and by their actions cause unacceptable residue levels in food

Pesticide use in Malaysia is also subject to the Environmental Quality (ScheduledWastes) Regulations, 1987 The objectives of these regulations are to control andmanage the generation, storage, transportation, recycling, treatment or destruction,and disposal of toxic and hazardous wastes.

Malaysia began active environmental management with enactment of theEnvironmental Quality Act, 1974 and the creation of the Department of theEnvironment in 1976 (Abdullah, 1995) The Environmental Quality Act wasamended in 1985 to include submission of Environmental Impact Assessment(EIA) reports to the Department of the Environment for proposed developmentprojects, thus moving the country toward a proactive, preventive strategy ofenvironmental management EIAs, which became mandatory in 1988, are used topredict potential environmental impacts from the proposed development There-after, mitigation measures can be identified and prescribed to minimize thepredicted impacts The Department of the Environment also regularly monitorsair and water quality throughout the country To monitor river water quality,samples are collected from 116 major rivers at 892 monitoring stations and, toassess marine water quality, there are an additional 229 sampling stations in coastaland estuarine areas (Abdullah, 1995) The majority of analyses for river and marinesamples are conducted in laboratories of the Department of Chemistry under theMinistry of Science, Technology, and the Environment (Abdullah, 1995) Currently,there is no national or regional monitoring program designed to identify andmeasure pesticide residues in the environment beyond those tasked with evaluatingpossible risk to humans

P E S T I C I D E R E S I D U E S I N T H E A Q U AT I C

E N V I R O N M E N T

Contamination of the environment by pesticides arises primarily from theirapplication Surface water contamination can occur as a result of spray drift fromaerial spraying or runoff from agricultural areas as a consequence of rain, and to

a lesser extent, leaching from the soil Hence, runoff water contains dissolvedpesticides as well as chemicals sorbed onto particulate matter Pesticide residuescan also be transported sorbed on airborne particles and then washed into theaquatic environment by rainfall Pesticides applied on fields have been known tovolatilize and be deposited in areas far removed from the point of application.Volatile pesticides have been observed to be more rapidly lost in tropical agro-ecosystems because of the high temperatures associated with this region Severalstudies involving volatile OC insecticides such as DDT and HCH have shownvolatilization to be a major route of dissipation of these chemicals from tropical

agro-ecosystems and other tropical environments (Abdullah et al., 1997) Ultimately

the ocean acts as the final reservoir for these chemicals

In addition to surface water, groundwater can also be contaminated by pesticideresidues as a result of leaching from the soil and the inherent interaction between

groundwater and contaminated surface water Contamination of the environment

by pesticides arises not only from their application but also from accidental orintentional discharges of pesticides and pesticide wastes and rinses from mixingareas (on the farm) and from manufacturing plants

There is at present no national or regional monitoring program designed toinvestigate pesticide residues in the environment, apart from those intended toevaluate possible risk to humans However, over the years some data have beenaccumulated from studies conducted by various groups and researchers Table 7.3provides an indication of the extent of contamination by OC pesticides in bothbiotic and abiotic components of the freshwater environment of Malaysia OCsare of particular concern due to their persistent nature, and their bio-accumulativeand toxic properties OC pesticide residues are commonly detected in the aquaticenvironment Pesticides, which have been banned or whose use has been restricted,e.g dieldrin, endrin, and DDT, continue to be detected in the environment due to

their persistent character In a recent study by Tan et al (1991), DDE, DDT, and

heptachlor were found in samples of water from almost every river surveyed inPeninsular Malaysia Endosulfan, an insecticide with a well-documented piscidalactivity, was also commonly detected As to be expected, higher levels of pesticideresidues were observed in the vicinity of agricultural land HCH, heptachlor, aldrin,and endosulfan were detected in sediments in a recent survey conducted in thevicinity of a rice growing area (Tan and Vijayaletchumy, 1994) Significant levels

of both HCH and endosulfan were due to current usage of these chemicals in ricefields

In general, there appears to be a decreasing trend in the levels of OC pesticidesdetected in the Malaysian aquatic environment This can be seen when a com-parison is made between earlier studies and more recent studies (see Table 7.3) ofMalaysia’s freshwater environment Additionally, this trend is apparent in relation

to similar studies conducted in India where OC insecticides, in particular HCHand DDT, have been the major pesticides for years Surveys in 1982 in Tanjong

-HCH in water These levels are comparable to similar studies conducted in India

(Ramesh et al., 1990) However, a recent survey by Tan et al (1991) showed

substan-tially less contamination This encouraging trend can be attributed to several factors,including the increasingly popular use of less persistent OP and carbamatepesticides in favor of the OC class Educational programs in the safe and effectiveuse of these chemicals conducted by the pesticide industry and the Department ofAgriculture and directed toward end users and suppliers of pesticides have alsocontributed to the observed trend

The marine environment, in particular near-shore coastal waters, has also beenobserved to be contaminated by OC pesticide residues The majority of Malaysia’sagricultural land is located in the vicinity of the western coastline of PeninsularMalaysia (Figure 7.1) Hence, agricultural runoff and spray drift allow thedeposition of applied pesticides into near-shore coastal waters In Malaysia, surveysconducted to measure pesticide residues in the marine environment have been