As a farmer, I can tell you authoritatively that the problem isn't the pesticides. It is the farmer.
Every pesticide will have instructions on how long you must wait after spraying before you consume the produce. Normally 14-21 days.
Very few farmers wait this duration. In fact, for things like Kales or spinach, most farmers will leave a small portion of the farm unsprayed. That is for their own consumption. What they have sprayed is sold to the market as early as two days after spraying. Bora harufu imeisha.
It's the government policies and taxation.
Case1.
A tomato/onion farmer in Kenya competes with tomato farmers from Tanzania, Uganda, Ethiopia who have free access to the Kenyan market whereas the Kenyan farmer cannot freely export produce to the same markets.
Cost of production
1.Casual labour cost per day 500kes, 5000Tzs-250kes, 9000ugx-300kes
2. Fertilizers 6000kes, 58000Tzs-2900kes,
3. Pesticides/Chemicals Ridomil 2250 Kes, Ivory 25000Tzs/1200kes
4. Access to virgin lands for cultivation
5. Access to water..... Tanzania has numerous lakes, rivers and mini irrigation schemes, Uganda has abundant rainfall and lots of water bodies
6.......
If the government cannot protect and support it's farmers, they will look for ways to cut corners to compete with the unfair competition from outsiders enjoying government subsidies and zero barriers to the Kenyan market