*3.2.1.7 Granules (G)*

Granular formulations are similar to Dust formulations and contain a toxicant (1–10% by weight) and an inert diluent, the major difference being particle size, with *granules* ranging from 20 to 100 mesh and *dusts* passing through 300 mesh screens. Granules are made from active ingredients, in many ways: (i) the toxicant (which is

*Pesticides: Chemistry, Manufacturing, Regulation, Usage and Impacts on Population in Kenya DOI: http://dx.doi.org/10.5772/intechopen.105826*

a liquid) may be added so as to impregnate the solid granules, which are then dried and thus completely released only when the granule breaks up after application, or (ii) the toxicant may be surface-coated on to granules using a volatile solvent; i.e. the toxicant, (liquid or solid), dissolves in volatile solvent, which evaporates from the formulation, or (iii) grinding the solid toxicant with inert diluents. The inert diluents for granular formulations can be *clays* or *organic materials* such as corncobs (e.g. Furadan - with *carbofuran* a.i. formulated with *grit material made from corncobs*), pecan shells, tobacco stems and walnut shells, respectively. Granules (mostly for soil and water surfaces) are less likely to drift unlike dust or liquid sprays and have less tendency to adhere to foliage.

#### *3.2.1.8 Water-dispersible granules (WGs)*

Water-dispersible granules (WGs), known as Dry *Flowables,* contain typically a toxicant (50–95%, w/w), a dispersant (e.g. surfactant), a binder and diluents. They are granules intended for application after disintegration and dispersion in water at the farm*.* They have low dust properties (due to larger particles) and exhibit good flowability. WGs are manufactured by blending and agglomerating a ground solid active ingredient together, with surfactants and other ingredients, mixed with water, then drying step to reduce moisture to a 1−2% range. A binder/an anti-caking agent/ carrier such as *inert clay* can be used, e.g. Greensperse® CA-N is an imported binder optimized as granules, which provide enough strength and resistance to abrasion to reduce dusting and maintain the granule's integrity until its application. When powder is agglomerated, particularly by wet granulation flowability is greatly improved. A high MW polyoxyethylene surfactant can be used in agglomeration.

#### *3.2.1.9 Ultra-low volume (ULV)*

Ultra-low volume (ULV) formulations are undiluted technical grade material or the original a.i. dissolved in a minimum amount of solvent, in case of a solid a.i. They are applied, e.g. by helicopter, without further dilution in an extremely fine spray generated by special aerial or ground spray equipment, and are useful for public health vectors and agricultural and forest pests. ULV applications offer several advantages, including high efficacy due to high directed concentrations at the target and absence of masking inert diluents/surfactants, compared with a normal formulation spray [77]. The technique is useful in treating large areas, e.g. a helicopter carrying 100 gallons of ULV-malathion, to spray 400–800 acres of rangeland before reloading. In Kenya, it is used in mosquito control programs, desert locust control and largescale wheat farms in Narok and Laikipia.

#### *3.2.1.10 Aerosols*

Aerosols are commonly used widely in Kenya for controlling resident flying and crawling insects such as mosquitoes, ants, termites and cockroaches in the domestic sectors. The active ingredient is dissolved in a *volatile solvent*, e.g. a *petroleum solvent,* and the resulting solution is atomized through a jet by means of a propellant. The propellant can be a *gas under pressure* or a *liquid that is gaseous* at atmospheric pressure conditions. Chlorofluorocarbons propellants have now been replaced by other environmentally friendly volatile liquids such as *butane, dimethyl ether, compressed carbon dioxide or nitrogen*.

#### *3.2.1.11 Controlled release (CR) formulations*

Controlled release (CR) formulations are recent innovations, where the pesticide is incorporated into a *carrier*, generally, a *polymeric material* and are diffusion-controlled [78]. They are microencapsulated formulations consisting of a solid or liquid inert containing an active ingredient surrounded by a plastic or starch coating [79]. The resulting capsules can be sold as *dispersible granules* (dry flowables) or as *liquid* formulations. Encapsulation enhances applicator safety while providing timed release of the active ingredient. Liquid forms of microencapsulates are further diluted with water and applied as sprays, forming suspensions in the spray tank and having many similar properties as liquid flowables. The rate of release of the pesticide is determined by the properties of the polymer as well as environmental factors. Polymers, e*.g. proteins, synthesized vinyl 2, 4-dichlorophenoxyacetate and vinyl 2-(2, 4, 5-trichlorophenoxy) propionate,* respectively, can be used. An example is the *2-Acryloxyethyl ester of 2, 4-D copolymerized with triethylamine methacrylamide*. There are mainly two types of CR formulations, i.e. the *Reservoir Devices* and the *Monolithic Devices*, respectively. The reservoir devices are made when the toxicant is enclosed in the capsules of a thin polymeric material to become microcapsules of 1–100 μm in diameter; e.g. *Penn Cap-M microcapsules* (methyl parathion product). The *Monolithic Devices* are made when the toxicant is uniformly dissolved or dispersed within the polymer matrix to become microparticles of 1–100 μm diameter or strips; e.g. *Alco No-Pest Strip* (with dichlorvos is the active ingredient), which is used widely in pet flea collars [80]. The manufacturing of these devices is highly mechanized and expensive and, therefore, they are not yet popular in Kenya. There are also other disadvantages including longer-lasting residues and potential toxicity to beneficial insects such as bees.

#### *3.2.1.12 Baits*

Baits can be very useful for achieving selective toxicity of insecticides against some species of insects. Spot application, i.e. where the bait is placed in selected places, which are accessible only to target species, permits use of insecticides in a safe manner with no environmental disruption and less human exposure. A bait formulation consists of a *carrier, toxicant and feeding stimulants*. Carriers are made from *laying mash, cracked corn, wheat bran, corn cob grits and peanut hull*, while feeding stimulants include *crude cotton seed oil, refined soybean oil, sucrose, coax brewers concentrate, malt extract, glucose, maltose, honey and wheat germ*. Several types of baits are available in the market, e.g. malathion 4% w/w bait formulated from crude cotton seed oil (5%) and sucrose (10%) on a laying mash carrier, among others [81, 82].

*Formulation labels-*after a formulation has been manufactured, a suitable package is used and labeling is done. What goes into the labels is important for trade purposes and includes sufficient information to inform the buyer about the quality, concentrations and safety of the product as well as any notable special features of the pesticide product. The concentration of the pesticide on the label is very important because it gives guidance on further dilution with water at the site of application. For dry formulations such as WPs, dust and granules, respectively, the insecticide concentration is expressed *as percentage of active ingredient* (a.i.) by weight in the formulations e.g. Diazinon® 50 W or 50WP means it is a formulation containing 50% diazinon (by wt) as the a.i and is a wettable powder formulation. For liquid formulations such as Solutions (S) and emulsifiable concentrates (EC), the concentration of the

*Pesticides: Chemistry, Manufacturing, Regulation, Usage and Impacts on Population in Kenya DOI: http://dx.doi.org/10.5772/intechopen.105826*

insecticide is expressed in pounds of a.i. /gallon or grams of a.i./Liter of formulation etc. Diazinon® 4E or Diazinon 4EC means it is an emulsifiable concentrate formulation containing 4 lb. of diazinon (or 4 g/L depending on units used in a particular country) in each gallon or liter of the formulation, respectively.

#### *3.2.2 Manufacturing of biopesticides in Kenya*

Biopesticides are derived from micro-organisms (bacteria, fungi, viruses, etc), plants (neem, pyrethrum, etc) and natural enemies of pests (parasitoids, predatory mites and pathogens). Additional substances under biopesticides are semiochemicals (e.g. insect sex pheromones), enzymes (proteins) and insect growth regulators. The biocontrol products presented in **Table 3** include twenty-seven (27) different products/formulations which are manufactured from nineteen (19) different active ingredients by nine (9) different companies in Kenya [11]. Biopesticides have become very popular in the horticultural sector, led by flowers, French beans, peas and avocadoes, which are grown mainly for export. The driving force behind this new shift


#### **Table 3.**

*Some biopesticides manufactured in Kenya.*

towards biopesticides is mainly the need to avoid the strict residue limits imposed by the importing countries in Europe.

## **4. Pesticide use and impacts in Kenya**

#### **4.1 Pesticide use in agriculture and its impacts**

Although developed countries consume 75% of the global pesticide in the market, it is the developing countries that will bear the heaviest burden of pesticides impact despite consuming just 22% [83–85], because of weaknesses in the regulatory mechanism and lack of education and awareness, especially among farmers. Apart from the long-term effects of pesticides, which are already known, several cases of severe impacts have been seen in Kenya including, (i) high mortalities caused by poisoning through suicides [86], (ii) high incidences of occupational exposure among farmers [4, 84, 86, 87], (iii) environmental degradation [26, 83, 84, 80–90], (iv) consumption of contaminated foods and water [26, 89, 91–95 ] and (v) misuse causing threats to wildlife, insects and other species [26, 83, 84, 89–90]. In Kenya, the increased amounts of pesticides being used and the reported potential human impacts, for example, cancer, which is now a major killer [83], seem to coincide, and this has raised concerns among the population. Many cases of acute pesticide poisoning, sometimes fatal, have been detected in people in the agricultural sector, where exposure to pesticides is highest [4, 84, 86, 87]. Even with low exposure, pesticides can cause serious consequences such as acute male infertility, cancers, abortions and other birth defects, and fetal malformations [84].

The rural population in Kenya constitutes approximately 80% of the total population; therefore, human and environmental health risks associated with pesticides are heavily experienced among this population since agriculture is mostly practiced in the rural areas [96]. The government has over the years put strategies to mitigate environmental impacts of pesticides, for example by the ratification of the Stockholm Convention in May 2004 and a national implementation plan in 2007 [97], which led to banning of most of the persistent OCs [11]. Banning of OCs can lead to recovery of affected species in nature [98]. However, a number of highly toxic OPs, carbamates, pyrethroids, neonicotinoids and fungicides, belonging to WHO I and II class, which have been banned in other countries such as the EU, have not been restricted or banned in Kenya [84]. There is, therefore, a dire need for risk assessment of all pesticides on the PCPB database for possible withdrawal or banning of the highly toxic ones.

Several studies on pesticide usage and impacts have been conducted following international best practices, in various agricultural regions in the country, which have revealed that the current group of pesticides used in Kenya are mostly highly toxic and pose threat to humans and the environment [84, 99–102]. Most of the pesticides are used intensively in certain regions that are traditionally agricultural zones, in the *North rift*, the *Central highlands*, the *South Rift*, *Eastern province*, as well as *Western* and *Nyanza provinces*, respectively, where specific types of crops are grown for local consumption and export; and it is in these regions where most studies have been done. In fact, several cases of pesticide misuse by farmers, occupational exposure and potential risks to human and drinking water have been documented since the year 2000. Two recent surveys were conducted in Trans-Nzoia County in Western Kenya which is the largest producer of maize in the country, producing at least 5 million bags
