The phrase "a substantial effect and" is correct and usable in written English.
It can be used when discussing the impact or influence of something in a formal or academic context.
Example: "The new policy is expected to have a substantial effect and improve overall productivity in the workplace."
Alternatives: "a significant impact and" or "a considerable influence and".
Table 7 shows that increasing generosity of maternity leave still has a substantial effect and that the main source of that effect is through job protection.
In particular, we tried to identify circumstances in which antibiotic therapy has a substantial effect and should be used to reduce the prevalence of colonization in an ICU.
The advantage of the method is that growth is terminated before confounders, such as selection (differential growth of mutants vs. parentals), can produce a substantial effect, and this and other confounders can in any case be reconstructed and measured and the mutation rate adjusted appropriately.
It is expected that cell membrane damage and biofilm inhibition would have a substantial effect on pathways and genes related to cell wall synthesis and metabolism.
T37A and I41A had a substantial effect on AM and AM2 potency.
The announcement of the withdrawal of co-proxamol in the UK has had a substantial effect on prescribing and on deaths from poisoning in England and Wales, particularly suicides.
Their participation in civil society, politics and post-conflict peace-building can have a substantial effect on outcomes and on the political environment.
As early and effective antimicrobial therapy has a substantial effect on bacterial eradication and patient survival [ 6, 31], optimal individual dosing of antibiotics is of particular importance.
(1) Family-Community Care interventions can have a substantial effect on neonatal and perinatal mortality.
Management had a substantial effect on habitat and echinoid community structure, as coral cover was significantly higher, macroalgal cover lower, and echinoid densities generally reduced on MPAs regardless of exposure intensity.
Hence, the results explicitly manifest that θ r is the indicator of the variation of fluid viscosity with temperature which has a substantial effect on f′ and hence on f″(1) (see Table 7 for details).
