House and Senate conferees yesterday refused to postpone new federal regulations limiting cotton dust in textile work places.

After a protracted wrangle between Sens. William Proxmire (D-Wis.) and Ernest F. Hollings (D.S.C), the conferees dropped from the $36 billion appropriation bill for the departments of Labor and Health, Education and Welfare a Senate provision that would have delayed that tough new cotton-dust limits until May 1.

Labor Secretary Ray Marshall put the standards into effect Sept. 4. Hollings and others wanted to delay them pending further study of the relation between cotton dust and "brown lung," a respiratory disease Marshall said already has caused severe illness in 35,000 cotton-industry workers.

The conferees agreed to order a further Labor Department study of the new standards to be completed in 1979, but without impeding implementation of the cotton-dust restrictions.

Conferees also agreed to provide 52.6 billion in fiscal 1979 for college grants to needy and middle-income students. The Senate originally voted $2.2 billion, the House $3.4 billion.

House conferees and HEW said the higher figure was needed to fund grants to middle-income families newly eligible for the college-aid program.

However, Senate Appropriations Committee Chairman Warren G. Magnuson (D-Wash.) initially balked at adding anything above $2.2 billion.He wanted to wait until it became clear whether the tuition tax credit, an alternative form of financial aid for middle-income students, would clear Congress. Carter opposes the tuition tax credit and wanted the extra funds voted for the grant program.

The final bill carried $57 billion in budget authority for various programs but directed HEW to cut $1 billion from that, for a maximum spending authority of $56 billion, by reducing frand and waste. This is below the President's budget request.

The only issue still unsettled in the bill is the dispute over the House anti-abortion provision, which sharply limits free federal abortions for low-income women under the Medicaid program. Conferees will go back to the Senate and House for further votes on the abortion issue.